EP0670814B1 - Precipitated silica - Google Patents

Precipitated silica Download PDF

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Publication number
EP0670814B1
EP0670814B1 EP94928935A EP94928935A EP0670814B1 EP 0670814 B1 EP0670814 B1 EP 0670814B1 EP 94928935 A EP94928935 A EP 94928935A EP 94928935 A EP94928935 A EP 94928935A EP 0670814 B1 EP0670814 B1 EP 0670814B1
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EP
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Prior art keywords
silica
silicate
amount
added
acidifying agent
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German (de)
French (fr)
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EP0670814A1 (en
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Yvonick Chevallier
Evelyne Prat
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Rhodia Chimie SAS
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Rhodia Chimie SAS
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
    • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/04—Ingredients treated with organic substances
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/32—Spheres
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/50—Agglomerated particles
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/11—Powder tap density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/14—Pore volume
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/16—Pore diameter
    • C01P2006/17—Pore diameter distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/19—Oil-absorption capacity, e.g. DBP values

Definitions

  • the present invention relates to new precipitated silicas, having in particular in the form of powder, beads substantially spherical or granular, their preparation process and their application as a reinforcing filler for elastomers.
  • precipitated silica has long been used as a filler reinforcing white in elastomers, in particular in tires.
  • the filler has a very good ability to be incorporated into the matrix when mixing with the elastomer (incorporability of the filler) and disintegrate or disintegrate in the form of a very fine powder (load disaggregation), and where, on the other hand, the powder resulting from the The aforementioned disaggregation can itself, in turn, disperse perfectly and homogeneously in the elastomer (dispersion of the powder).
  • silica particles have an unfortunate tendency in the elastomer matrix to agglomerate between them.
  • These silica / silica interactions have the harmful consequence of limiting the reinforcing properties at a level significantly lower than it would theoretically possible to achieve if all silica / elastomer interactions likely to be created during the mixing operation, were actually obtained (this theoretical number of silica / elastomer interaction being, like this is well known, directly proportional to the external surface, of silica used).
  • silica / silica interactions tend, in the raw state, to increase the stiffness and consistency of the mixtures, thus making their use more difficult.
  • the object of the present invention is to obviate the aforementioned drawbacks and to solve the aforementioned problem.
  • the invention relates to new precipitated silicas which are generally in the form of powder, beads substantially spherical or, possibly, of granules, and which, while being able to present relatively large in size, have dispersibility (and deagglomeration) and very satisfactory reinforcing properties.
  • the main object of the invention consists of new precipitated silicas having dispersibility (and deagglomeration) properties and properties very satisfactory reinforcing, said silicas preferably having a relatively large size.
  • the BET specific surface is determined according to the BRUNAUER - EMMET - TELLER method described in "The journal of the American Chemical Society”, Vol. 60, page 309, February 1938 and corresponding to NFT 45007 (November 1987).
  • the CTAB specific surface is the external surface determined according to the standard NFT 45007 (November 1987) (5.12).
  • the DOP oil intake is determined according to standard NFT 30-022 (March 1953) using dioctylphthalate.
  • the packed filling density (DRT) is measured according to the standard NFT-O30100.
  • the pore volumes given are measured by poros mercury imetry, the pore diameters being calculated by the relation of WASHBURN with a theta contact angle equal to 130 ° and a tension surface gamma equal to 484 Dynes / cm (MICROMERITICS porosimeter 9300).
  • the ability to disperse and deagglomerate silicas according to the invention can be quantified by means of a specific test of disaggregation.
  • the value of the median diameter ⁇ 50 that is obtained is lower the higher the silica has a high deagglomeration capacity.
  • the ratio (10 ⁇ volume of suspension introduced (in ml)) / optical density of the suspension detected by the granulometer is also determined (this optical density is of the order of 20). This report is indicative of the level of fines, that is to say the rate of particles smaller than 0.1 ⁇ m which are not detected by the granulometer.
  • This ratio called ultrasound disaggregation factor (F D ), is all the higher as the silica has a high deagglomeration ability.
  • silica according to the invention therefore resides in the distribution, or distribution, of the volume porous, and more particularly in the distribution of the pore volume which is generated by pores with diameters less than or equal to 400 ⁇ .
  • This last volume corresponds to the useful pore volume of the fillers which are used in the reinforcement of elastomers.
  • Analysis of the porograms shows that the silicas according to the invention are such that less than 50%, especially less than 40%, and in in certain cases, less than 30%, of said useful pore volume is constituted by pores with a diameter in the range of 175 to 275 ⁇ .
  • the silicas according to the invention have an ultrasonic deagglomeration factor (F D ) greater than 3.0 ml, for example greater than 3.9 ml.
  • the silicas according to the invention generally have a BET specific surface (S BET ) of between 100 and 210 m 2 / g, in particular between 100 and 180 m 2 / g.
  • S BET BET specific surface
  • the silicas have an S BET / S CTAB ratio of between 1.0 and 1.2, that is to say that the silicas have a low microporosity.
  • the silica has an S BET / S CTAB ratio greater than 1.2, for example between 1.21 and 1.4, that is to say that the silicas have a microporosity relatively high.
  • the silicas according to the invention generally have a DOP oil intake between 150 and 400 ml / 100 g, more particularly between 180 and 350 ml / 100 g, for example between 200 and 310 ml / 100 g.
  • the silicas according to the invention are in the form of powder, substantially spherical or possibly granular balls and are in particular characterized by the fact that, while having a relatively small size high, they have an ability to disaggregate and disperse quite remarkable and good reinforcing properties. They present thus an aptitude for deagglomeration and dispersion advantageously larger, with identical or similar specific surface and identical size or close to that of the silicas of the prior art.
  • the silica powders according to the invention have a average size greater than 15 ⁇ m, in particular between 20 and 150 ⁇ m, for example between 30 and 100 ⁇ m.
  • the packed filling density (DRT) of said powders is, in general, at least 0.17, and, for example, between 0.2 and 0.3.
  • Said powders generally have a total pore volume of at least 2.5 cm 3 / g, and more particularly between 3 and 5 cm 3 / g.
  • the substantially spherical balls according to the invention have an average size of at least 80 ⁇ m.
  • this average size of the beads is at least 100 ⁇ m, for example at least 150 ⁇ m; she is usually at least plus 300 ⁇ m and is preferably between 100 and 270 ⁇ m.
  • This average size is determined according to standard NF X 11507 (December 1970) by dry sieving and determination of the diameter corresponding to a cumulative refusal of 50%.
  • the packed filling density (DRT) of said balls is, in general, at least 0.17, and, for example, between 0.2 and 0.32.
  • They generally have a total pore volume of at least 2.5 cm 3 / g, and more particularly, between 3 and 5 cm 3 / g.
  • Such a silica also constitutes a privileged precursor for the synthesis of powders and granules according to the invention.
  • These beads advantageously have a median diameter ( ⁇ 50 ), after deagglomeration with ultrasound, less than 3 ⁇ m and a deagglomeration factor with ultrasound (F D ) greater than 8 ml, for example 12 ml.
  • the dimensions of the granules according to the invention are at least minus 1 mm, in particular between 1 and 10 mm, along the axis of their plus large dimension (length).
  • Said granules can be in the most diverse forms.
  • the packed filling density (DRT) of said granules is in general at least 0.27 and can be up to 0.37.
  • They generally have a total pore volume of at least 1 cm 3 / g, and, more particularly, between 1.5 and 2 cm 3 / g.
  • the process concerned is a precipitation silica synthesis process, that is to say that a acidifying agent on an alkali metal silicate M.
  • acidifying agent and silicate are made in a well known manner in itself. It may be recalled that a acidifying agent is generally used strong mineral acid such as sulfuric acid, nitric acid or acid hydrochloric acid, or an organic acid such as acetic acid, formic acid or carbonic acid.
  • silicate any common form of silicates such as metasilicates, disilicates and advantageously a silicate of alkali metal M in which M is sodium or potassium.
  • acid is used sulfuric, and, as silicate, sodium silicate.
  • the latter generally has a SiO 2 / Na 2 O molar ratio of between 2 and 4, more particularly between 3.0 and 3.7.
  • the precipitation takes place in a specific manner according to the following steps.
  • a base stock which comprises silicate.
  • the amount of silicate present in this initial base stock does not advantageously represent only part of the total amount of silicate involved in the reaction.
  • the silicate concentration in the initial base stock is not more than 11 g / l and, possibly not more than 8 g / l.
  • the initial base stock may include an electrolyte. Nevertheless, preferably no electrolyte is used during the preparation process according to the invention; in particular, preferably, the initial base stock does not includes no electrolyte.
  • electrolyte is understood here in its normal acceptance, that is to say that it means any ionic or molecular substance which, when in solution, decomposes or dissociates to form ions or particles loaded. Mention may be made, as electrolyte, of a salt from the group of metal salts alkaline and alkaline earth metals, especially the salt of the starting silicate metal and the acidifying agent, for example sodium sulfate in the case of the reaction of a sodium silicate with sulfuric acid.
  • the second step is to add the acidifying agent to the base. of composition described above.
  • the acidifying agent is added to said initial base stock until at least 50% of the amount of M 2 O present in said initial base stock is neutralized.
  • the acidifying agent is added to said initial base stock until 50 to 99% of the amount of M 2 O present in said initial base stock is neutralized.
  • the acidifying agent can be diluted or concentrated; his normality can be between 0.4 and 36 N, for example between 0.6 and 1.5 N.
  • the acidifying agent is sulfuric acid
  • its concentration is preferably between 40 and 180 g / l, for example between 60 and 130 g / l.
  • the amount of acidifying agent added is such that 80 to 99%, for example 85 to 97%, of the amount of M 2 O added is neutralized.
  • step (iii) it is possible to carry out the simultaneous addition of acidifying agent and silicate to a first level of pH of the reaction medium, pH 1 , then to a second level of pH of the reaction medium, pH 2 , such as 7 ⁇ pH 2 ⁇ pH 1 ⁇ 9.
  • the acidifying agent used during step (iii) can be diluted or concentrated; her normality can be between 0.4 and 36 N, for example between 0.6 and 1.5 N.
  • this acidifying agent is sulfuric acid
  • its concentration is preferably between 40 and 180 g / l, for example between 60 and 130 g / l.
  • the alkali metal silicate M added during step (iii) has a concentration expressed as silica of between 40 and 330 g / l, for example between 60 and 250 g / l.
  • this ripening possibly by example last from 1 to 60 minutes, in particular from 5 to 30 minutes.
  • reaction medium an additional amount of acidifying agent.
  • This addition is generally carried out until a pH value of the reaction medium of between 3 and 6.5, preferably between 4 and 5.5, is obtained.
  • it makes it possible to neutralize the entire quantity of M 2 O added during step (iii) and to adjust the pH of the final silica to the desired value for a given application.
  • the acidifying agent used during this addition is generally identical to that used during step (iii) of the preparation process according to the invention.
  • the temperature of the reaction medium is usually between 60 and 98 ° C.
  • step (ii) the addition of acidifying agent during step (ii) is carried out in an initial base stock whose temperature is between 60 and 96 ° C.
  • the reaction is carried out at a constant temperature between 75 and 96 ° C.
  • the end of reaction temperature is higher than the temperature start of reaction: thus, the temperature is maintained at the start of the reaction preferably between 70 and 96 ° C, then the temperature is increased during reaction in a few minutes, preferably up to a value between 80 and 98 ° C, value at which it is maintained until the end of the reaction.
  • a slurry is obtained.
  • silica which is then separated (liquid-solid separation). This separation generally consists of filtration, followed by washing if necessary.
  • the filtration can be done by any suitable method, for example by filter press or belt filter or rotary vacuum filter.
  • the precipitated silica suspension thus recovered (filtration cake) is then dried.
  • This drying can be done by any means known per se.
  • the drying is carried out by atomization.
  • any suitable type of atomizer can be used, in particular atomizers with turbines, nozzles, liquid pressure or two fluids.
  • the suspension to be dried has a dry matter content greater than 18% by weight, preferably more than 20% by weight.
  • the drying is then generally carried out at by means of a turbine atomizer or, preferably, nozzles.
  • the precipitated silica capable of being obtained according to this variant of the process generally takes the form of beads substantially spherical, preferably with an average size of at least 80 ⁇ m.
  • This dry matter content can be obtained directly by filtration using a suitable filter giving a filter cake with the right content.
  • Another method consists, after filtration, at a later stage of the process, adding dry matter, for example silica under the cake pulverulent form, so as to obtain the necessary content.
  • the cake thus obtained is not, in general, in conditions allowing atomization especially because of its too high viscosity.
  • the cake is then subjected to an operation of disintegration.
  • This operation can be done by passing the cake through a grinder of colloidal or ball type.
  • aluminum especially in the form sodium aluminate during the process as described in the application for Patent FR-A-2536380, the teaching of which is incorporated here. This addition can be done in particular at the time of the disintegration.
  • a grinding step can be carried out on the recovered product, in particular on the product obtained by drying the suspension having a dry matter content greater than 18% by weight.
  • Silica precipitate which is then likely to be obtained generally occurs in the form of a powder, preferably of average size of at least 15 ⁇ m, in particular between 20 and 150 ⁇ m, for example between 30 and 100 ⁇ m.
  • Products ground to the desired particle size can be separated from any non-conforming products using, for example, vibrating screens with appropriate mesh sizes, and non-conforming products as well recovered be returned to grinding.
  • the suspension to be dried has a dry matter content of less than 18% in weight.
  • the drying is then generally carried out by means of an atomizer with turbines or nozzles.
  • Precipitated silica which can then be obtained according to this variant of the invention is generally in the form of a powder, preferably of average size of at least 15 ⁇ m, in particular between 20 and 150 ⁇ m, for example between 30 and 100 ⁇ m.
  • a disintegration operation can also be carried out here.
  • the dried product in particular from a suspension having a rate dry matter less than 18% by weight
  • ground may, according to another variant of the process of the invention, be subjected to an agglomeration step.
  • agglomeration is meant here any process which makes it possible to link them finely divided objects to bring them in the form of more objects large size and mechanically resistant.
  • These processes include direct compression, track granulation wet (i.e. with the use of a binder such as water, silica slurry, ...), extrusion and, preferably, dry compaction.
  • the precipitated silica capable of being obtained according to this variant of the process is advantageously in the form of granules, preferably at least 1 mm in size, in particular between 1 and 10 mm.
  • the products can be calibrated to a desired size, for example by sieving, then packaged for use future.
  • the powders, as well as the beads, of precipitated silica obtained by the method of the invention thus offer the advantage, among other things, of accessing simple, effective and economical with granules as mentioned above, in particular by conventional shaping operations, such as for example a granulation or compaction, without the latter causing degradations likely to mask or even annihilate the properties intrinsic reinforcers attached to these powders, as may be the case in the prior art by using conventional powders.
  • the silicas according to the invention find a particularly application interesting in the reinforcement of elastomers, natural or synthetic, and including tires. They give these elastomers a significant improvement in their mechanical properties, such as elongation at breaking, breaking and tearing resistance, while providing them with very satisfactory rheological properties.
  • a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.
  • the silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l.
  • the solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C.
  • a sulfuric acid solution with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.
  • the instantaneous neutralization rate is 92%, that is to say that 92% of the amount of Na 2 O added (per minute) are neutralized.
  • the consolidation rate, after this simultaneous addition, is equal to 19.5.
  • a precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).
  • This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.
  • the silica P1 is subjected to the deagglomeration test as defined earlier in the description.
  • a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.
  • the silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l.
  • the solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C.
  • a sulfuric acid solution with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.
  • the instantaneous neutralization rate is 93%, that is to say that 93% of the amount of Na 2 O added (per minute) are neutralized.
  • the consolidation rate, after this simultaneous addition, is equal to 19.2.
  • a precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87.1% (therefore a material content 12.9% by weight).
  • This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.
  • the silica P2 is subjected to the deagglomeration test as defined earlier in the description.
  • a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 5 g / l.
  • the silicate concentration expressed as SiO 2 in the initial base stock is therefore 5 g / l.
  • the solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C.
  • a sulfuric acid solution with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.
  • the instantaneous neutralization rate is 92%, that is to say that 92% of the amount of Na 2 O added (per minute) are neutralized.
  • the consolidation rate, after this simultaneous addition, is equal to 39.0.
  • a precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).
  • This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.
  • the silica P3 is subjected to the deagglomeration test as defined earlier in the description.
  • a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.
  • the silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l.
  • the solution is then brought to a temperature of 85 ° C. while keeping it under stirring.
  • a sulfuric acid solution with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; the temperature of the reaction medium is maintained at 85 ° C. during the addition of the sulfuric acid solution; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.
  • the temperature of the reaction medium is maintained at 85 ° C. for the 50 first minutes of simultaneous addition; it is then brought from 85 to 90 ° C in 5 min, then maintained at 90 ° C until the end of the reaction.
  • the instantaneous neutralization rate is 90%, that is to say that 90% of the amount of Na 2 O added (per minute) are neutralized.
  • the consolidation rate, after this simultaneous addition, is equal to 19.5.
  • reaction medium is then left to mature for 10 min (with stirring, at 90 ° C).
  • a precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).
  • This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.
  • the silica P4 is subjected to the deagglomeration test as defined earlier in the description.
  • a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.
  • the silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l.
  • the solution is then brought to a temperature of 80 ° C. while keeping it under stirring. Then there is introduced, for 3 min and 20 s, a sulfuric acid solution, with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; the temperature of the reaction medium is maintained at 80 ° C. during the addition of the sulfuric acid solution; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.
  • the temperature of the reaction medium is maintained at 80 ° C. for the 50 first minutes of simultaneous addition; it is then brought from 80 to 95 ° C in 7 min, then maintained at 95 ° C until the end of the reaction.
  • the instantaneous neutralization rate is 90%, that is to say that 90% of the amount of Na 2 O added (per minute) are neutralized.
  • the consolidation rate, after this simultaneous addition, is equal to 19.5.
  • reaction medium is then left to mature for 10 min (with stirring, at 95 ° C).
  • a precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).
  • This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.
  • the silica P5 is subjected to the deagglomeration test as defined earlier in the description.
  • the silicate concentration expressed as SiO 2 in the initial base stock is therefore 7.1 g / l.
  • the solution is then brought to a temperature of 95 ° C. while keeping it under stirring. The whole reaction is carried out at 95 ° C. Then there is introduced, for 3 min and 20 s, a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 5.4 l / min; at the end of this addition, the neutralization rate of the base stock is 67%, that is to say that 67% of the amount of Na 2 O present in the initial base stock is neutralized.
  • the instantaneous neutralization rate is 83%, that is to say that 83% of the amount of Na 2 O added (per minute) are neutralized.
  • the consolidation rate, after this simultaneous addition, is equal to 17.1.
  • reaction medium is then left to mature for 10 min (with stirring, at 95 ° C)
  • a precipitated silica slurry is thus obtained which is filtered and washed with using a filter press so that a cake is finally recovered silica with a loss on ignition of 78% (therefore a dry matter rate of 22% in weight).
  • This cake is then fluidized by mechanical and chemical action (addition of a quantity of sodium aluminate corresponding to a weight ratio Al / SiO 2 of 3000 ppm). After this disintegration operation, a pumpable cake is obtained, with a pH equal to 6.7, which is then atomized by means of a nozzle atomizer.
  • the silica P6 is subjected to the deagglomeration test as defined earlier in the description.
  • the silicate concentration expressed as SiO 2 in the initial base stock is therefore 5 g / l.
  • the solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C. with stirring. Then, for 3 min and 20 s, dilute sulfuric acid, with a density at 20 ° C. equal to 1.050, is introduced therein at a flow rate of 4.8 l / min; at the end of this addition, the neutralization rate of the base stock is 91%, that is to say 91% of the amount of Na 2 O present in the initial base stock is neutralized.
  • the instantaneous neutralization rate is 92%, that is to say that 92% of the amount of Na 2 O added (per minute) are neutralized.
  • the consolidation rate, after this simultaneous addition, is equal to 17.5.
  • silicate is stopped and continues to introduce dilute sulfuric acid so as to decrease the value of pH of the reaction medium up to a value equal to 4.4 in 7 min.
  • a precipitated silica slurry is thus obtained which is filtered and washed with using a filter press so that a cake is finally recovered silica with a loss on ignition of 81% (therefore a dry matter rate of 19% in weight).
  • This cake is then fluidized by mechanical and chemical action (addition of a quantity of sodium aluminate corresponding to an Al / SiO 2 weight ratio of 2500 ppm and addition of sulfuric acid). After this disintegration operation, a pumpable cake is obtained, with a pH equal to 6.5, which is then atomized by means of a nozzle atomizer.
  • the silica P7 is subjected to the deagglomeration test as defined earlier in the description.
  • This example illustrates the use and behavior of silicas according to the invention and prior art silicas in a formulation for rubber industrial.
  • the formulations are prepared as follows:
  • the discharge of the mixer takes place when the temperature of the chamber reaches 165 ° C. (that is to say, approximately t o + 5 min).
  • the mixture is introduced into a cylinder mixer, maintained at 30 ° C., to be calendered there. CBS, DPG and sulfur are introduced into this mixer.
  • the final mixture is calendered in the form of sheets 2.5 to 3 mm thick.
  • the measurements are carried out on the formulations in the raw state at 150 ° C.
  • the measurements are carried out on the vulcanized formulations.
  • Vulcanization is carried out by bringing the formulations to 150 ° C. for 40 minutes.
  • the silicas according to the invention lead to the weakest 100% modules, evidence of better dispersion of silica.
  • the highest reinforcing power of silicas according to the invention is in particular confirmed by the higher values obtained for the breaking strength and for tearing and for elongation at break.

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Abstract

Novel silicas in the form of powder and spherical beads or granules. The silicas are characterized by having a specific CTAB surface of 100-140 m2/g, a small median diameter, following disaggregation by ultrasound means, and optionally, a porous distribution so that the porous volume occupied by the pores whose diameter is 175-275 ANGSTROM is less than 55% of the porous volume occupied by the pores having diameters of 400 ANGSTROM or less. The invention also concerns a method for the preparation of said silicas and their use as reinforcing fillers for elastomers.

Description

La présente invention concerne de nouvelles silices précipitées, se présentant en particulier sous forme de poudre, de billes sensiblement sphériques ou de granulés, leur procédé de préparation et leur application comme charge renforçante pour les élastomères.The present invention relates to new precipitated silicas, having in particular in the form of powder, beads substantially spherical or granular, their preparation process and their application as a reinforcing filler for elastomers.

On sait que la silice précipitée est utilisée depuis longtemps comme charge blanche renforçante dans les élastomères, en particulier dans les pneumatiques.We know that precipitated silica has long been used as a filler reinforcing white in elastomers, in particular in tires.

Cependant, comme toute charge renforçante, il convient qu'elle puisse se manipuler d'une part, et surtout s'incorporer d'autre part, facilement dans les mélanges.However, like any reinforcing filler, it should be able to to handle on the one hand, and above all to be incorporated on the other hand, easily in the mixtures.

On sait, d'une manière générale, que pour obtenir les propriétés de renforcement optimales conférées par une charge, il convient que cette dernière soit présente dans la matrice élastomère sous une forme finale qui soit à la fois la plus finement divisée possible et répartie de la façon la plus homogène possible. Or, de telles conditions ne peuvent être réalisées que dans la mesure où, d'une part, la charge présente une très bonne aptitude à s'incorporer dans la matrice lors du mélange avec l'élastomère (incorporabilité de la charge) et à se désagréger ou se désagglomérer sous la forme d'une poudre très fine (désagrégation de la charge), et où, d'autre part, la poudre issue du processus de désagrégation précité peut elle-même, à son tour, se disperser parfaitement et de façon homogène dans l'élastomère (dispersion de la poudre).We know, in general, that to obtain the properties of optimal reinforcement conferred by a load, the latter should either present in the elastomer matrix in a final form which is both the as finely divided as possible and distributed as homogeneously as possible. However, such conditions can only be fulfilled insofar as, on the other hand, the filler has a very good ability to be incorporated into the matrix when mixing with the elastomer (incorporability of the filler) and disintegrate or disintegrate in the form of a very fine powder (load disaggregation), and where, on the other hand, the powder resulting from the The aforementioned disaggregation can itself, in turn, disperse perfectly and homogeneously in the elastomer (dispersion of the powder).

De plus, pour des raisons d'affinités réciproques, les particules de silice ont une fâcheuse tendance, dans la matrice élastomère, à s'agglomérer entre elles. Ces interactions silice/silice ont pour conséquence néfaste de limiter les propriétés de renforcement à un niveau sensiblement inférieur à celui qu'il serait théoriquement possible d'atteindre si toutes les interactions silice/élastomère susceptibles d'être créées pendant l'opération de mélange, étaient effectivement obtenues (ce nombre théorique d'interaction silice/élastomère étant, comme cela est bien connu, directement proportionnel à la surface externe, de la silice utilisée).In addition, for reasons of mutual affinities, the silica particles have an unfortunate tendency in the elastomer matrix to agglomerate between them. These silica / silica interactions have the harmful consequence of limiting the reinforcing properties at a level significantly lower than it would theoretically possible to achieve if all silica / elastomer interactions likely to be created during the mixing operation, were actually obtained (this theoretical number of silica / elastomer interaction being, like this is well known, directly proportional to the external surface, of silica used).

En outre, de telles interactions silice/silice tendent, à l'état cru, à augmenter la raideur et la consistance des mélanges, rendant ainsi leur mise en oeuvre plus difficile. In addition, such silica / silica interactions tend, in the raw state, to increase the stiffness and consistency of the mixtures, thus making their use more difficult.

Le problème se pose de disposer de charges qui, tout en pouvant avoir une taille relativement élevée, présentent une très bonne aptitude à la dispersion dans les élastomères.The problem arises of having charges which, while being able to have a relatively large size, have very good dispersibility in elastomers.

La présente invention a pour but d'obvier aux inconvénients précités et de résoudre le problème sus-mentionné.The object of the present invention is to obviate the aforementioned drawbacks and to solve the aforementioned problem.

Plus précisément, l'invention concerne de nouvelles silices précipitées qui se présentent, en général, sous forme de poudre, de billes sensiblement sphériques ou, éventuellement, de granulés, et qui, tout en pouvant présenter une taille relativement élevée, ont une aptitude à la dispersion (et à la désagglomération) et des propriétés renforçantes très satisfaisantes.More specifically, the invention relates to new precipitated silicas which are generally in the form of powder, beads substantially spherical or, possibly, of granules, and which, while being able to present relatively large in size, have dispersibility (and deagglomeration) and very satisfactory reinforcing properties.

Elle a également pour but de proposer un procédé de préparation de ces silices précipitées.It also aims to propose a process for preparing these precipitated silicas.

Elle est relative enfin à l'utilisation desdites silices précipitées comme charge renforçante pour élastomères, à qui elles confèrent de très bonnes propriétés mécaniques.Finally, it relates to the use of said precipitated silicas as reinforcing filler for elastomers, to which they confer very good mechanical properties.

Le principal objet de l'invention consiste en de nouvelles silices précipitées ayant une aptitude à la dispersion (et à la désagglomération) et des propriétés renforçantes très satisfaisantes, lesdites silices présentant de préférence une taille relativement élevée.The main object of the invention consists of new precipitated silicas having dispersibility (and deagglomeration) properties and properties very satisfactory reinforcing, said silicas preferably having a relatively large size.

Dans l'exposé qui suit, la surface spécifique BET est déterminée selon la méthode de BRUNAUER - EMMET - TELLER décrite dans "The journal of the American Chemical Society", Vol. 60, page 309, février 1938 et correspondant à la norme NFT 45007 (novembre 1987).In the following description, the BET specific surface is determined according to the BRUNAUER - EMMET - TELLER method described in "The journal of the American Chemical Society ", Vol. 60, page 309, February 1938 and corresponding to NFT 45007 (November 1987).

La surface spécifique CTAB est la surface externe déterminée selon la norme NFT 45007 (novembre 1987) (5.12).The CTAB specific surface is the external surface determined according to the standard NFT 45007 (November 1987) (5.12).

La prise d'huile DOP est déterminée selon la norme NFT 30-022 (mars 1953) en mettant en oeuvre le dioctylphtalate.The DOP oil intake is determined according to standard NFT 30-022 (March 1953) using dioctylphthalate.

La densité de remplissage à l'état tassé (DRT) est mesurée selon la norme NFT-O30100.The packed filling density (DRT) is measured according to the standard NFT-O30100.

On précise enfin que les volumes poreux donnés sont mesurés par poros imétrie au mercure, les diamètres de pores étant calculés par la relation de WASHBURN avec un angle de contact théta égal à 130° et une tension superficielle gamma égale à 484 Dynes/cm (porosimètre MICROMERITICS 9300).Finally, it is specified that the pore volumes given are measured by poros mercury imetry, the pore diameters being calculated by the relation of WASHBURN with a theta contact angle equal to 130 ° and a tension surface gamma equal to 484 Dynes / cm (MICROMERITICS porosimeter 9300).

L'aptitude à la dispersion et à la désagglomération des silices selon l'invention peut être quantifiée au moyen d'un test spécifique de désagglomération.The ability to disperse and deagglomerate silicas according to the invention can be quantified by means of a specific test of disaggregation.

Le test de désagglomération est réalisé selon le protocole suivant :

  • la cohésion des agglomérats est appréciée par une mesure granulométrique (par diffraction laser), effectuée sur une suspension de silice préalablement désagglomérée par ultra-sonification ; on mesure ainsi l'aptitude à la désagglomération de la silice (rupture des objets de 0,1 à quelques dizaines de microns). La désagglomération sous ultra-sons est effectuée à l'aide d'un sonificateur VIBRACELL BIOBLOCK (600 W), équipé d'une sonde de diamètre 19 mm. La mesure granulométrique est effectuée par diffraction laser sur un granulomètre SYMPATEC.
    • The disagglomeration test is carried out according to the following protocol:
  • the cohesion of the agglomerates is assessed by a particle size measurement (by laser diffraction), carried out on a suspension of silica previously deagglomerated by ultra-sonification; the aptitude for deagglomeration of the silica is thus measured (rupture of objects from 0.1 to a few tens of microns). The deagglomeration under ultrasound is carried out using a VIBRACELL BIOBLOCK sonicator (600 W), equipped with a 19 mm diameter probe. The particle size measurement is carried out by laser diffraction on a SYMPATEC granulometer.

    • On pèse dans un pilulier (hauteur : 6 cm et diamètre : 4 cm) 2 grammes de silice et l'on complète à 50 grammes par ajout d'eau permutée : on réalise ainsi une suspension aqueuse à 4 % de silice qui est homogénéisée pendant 2 minutes par agitation magnétique. On procède ensuite à la désagglomération sous ultra-sons comme suit : la sonde étant immergée sur une longueur de 4 cm, on règle la puissance de sortie de manière à obtenir une déviation de l'aiguille du cadran de puissance indiquant 20 % (ce qui correspond à une énergie dissipée par l'embout de la sonde de 120 Watt/cm2). La désagglomération est effectuée pendant 420 secondes. On réalise ensuite la mesure granulométrique après avoir introduit dans la cuve du granulomètre un volume (exprimé en ml) connu de la suspension homogénéisée.Weigh into a pillbox (height: 6 cm and diameter: 4 cm) 2 grams of silica and make up to 50 grams by adding deionized water: an aqueous suspension of 4% silica is thus produced which is homogenized for 2 minutes by magnetic stirring. Then deagglomeration under ultrasound is carried out as follows: the probe being immersed over a length of 4 cm, the output power is adjusted so as to obtain a deviation of the pointer from the power dial indicating 20% (which corresponds to an energy dissipated by the tip of the probe of 120 Watt / cm 2 ). The deagglomeration is carried out for 420 seconds. The particle size measurement is then carried out after having introduced into the tank of the particle size analyzer a known volume (expressed in ml) of the homogenized suspension.

    La valeur du diamètre médian ⊘50 que l'on obtient est d'autant plus faible que la silice présente une aptitude à la désagglomération élevée. On détermine également le rapport (10 x volume de suspension introduite (en ml))/densité optique de la suspension détectée par le granulomètre (cette densité optique est de l'ordre de 20). Ce rapport est indicatif du taux de fines, c'est-à-dire du taux de particules inférieures à 0,1 µm qui ne sont pas détectées par le granulomètre. Ce rapport appelé facteur de désagglomération aux ultra-sons (FD) est d'autant plus élevé que la silice présente une aptitude à la désagglomération élevée. The value of the median diameter ⊘ 50 that is obtained is lower the higher the silica has a high deagglomeration capacity. The ratio (10 × volume of suspension introduced (in ml)) / optical density of the suspension detected by the granulometer is also determined (this optical density is of the order of 20). This report is indicative of the level of fines, that is to say the rate of particles smaller than 0.1 μm which are not detected by the granulometer. This ratio, called ultrasound disaggregation factor (F D ), is all the higher as the silica has a high deagglomeration ability.

    Il est maintenant proposé selon l'invention une nouvelle silice précipitée caractérisée en ce qu'elle possède :

    • une surface spécifique CTAB (SCTAB) comprise entre 1.00 et 140 m2/g, de préférence entre 100 et 135 m2/g.
    • une distribution poreuse telle que le volume poreux constitué par les pores dont le diamètre est compris entre 175 et 275 Å représente moins de 50 % du volume poreux constitué par les pores de diamètres inférieurs ou égaux à 400 Å,
    • un diamètre médian (Ø50), après désagglomération aux ultra-sons, inférieur à 4,5 µm, de préférence inférieur à 4 µm, par exemple inférieur à 3,8 µm.
    A new precipitated silica is now proposed according to the invention, characterized in that it has:
    • a CTAB specific surface (S CTAB ) of between 1.00 and 140 m 2 / g, preferably between 100 and 135 m 2 / g.
    • a porous distribution such that the pore volume constituted by the pores whose diameter is between 175 and 275 Å represents less than 50% of the pore volume constituted by the pores with diameters less than or equal to 400 Å,
    • a median diameter (Ø 50 ), after deagglomeration with ultrasound, less than 4.5 μm, preferably less than 4 μm, for example less than 3.8 μm.

    Une des caractéristiques de la silice selon l'invention réside donc dans la distribution, ou répartition, du volume poreux, et plus particulièrement dans la distribution du volume poreux qui est généré par les pores de diamètres inférieurs ou égaux à 400 Å. Ce dernier volume correspond au volume poreux utile des charges qui sont utilisées dans le renforcement des élastomères. L'analyse des porogrammes montre que les silices selon l'invention sont telles que moins de 50 %, en particulier moins de 40 %, et dans certains cas, moins de 30 %, dudit volume poreux utile est constitué par des pores dont le diamètre est compris dans le plage de 175 à 275 Å.One of the characteristics of silica according to the invention therefore resides in the distribution, or distribution, of the volume porous, and more particularly in the distribution of the pore volume which is generated by pores with diameters less than or equal to 400 Å. This last volume corresponds to the useful pore volume of the fillers which are used in the reinforcement of elastomers. Analysis of the porograms shows that the silicas according to the invention are such that less than 50%, especially less than 40%, and in in certain cases, less than 30%, of said useful pore volume is constituted by pores with a diameter in the range of 175 to 275 Å.

    En général, les silices selon l'invention possèdent un facteur de désagglomération aux ultra-sons (FD) supérieur à 3,0 ml, par exemple supérieur à 3,9 ml.In general, the silicas according to the invention have an ultrasonic deagglomeration factor (F D ) greater than 3.0 ml, for example greater than 3.9 ml.

    Les silices selon l'invention possèdent généralement une surface spécifique BET (SBET) comprise entre 100 et 210 m2/g, en particulier entre 100 et 180 m2/g.The silicas according to the invention generally have a BET specific surface (S BET ) of between 100 and 210 m 2 / g, in particular between 100 and 180 m 2 / g.

    Selon une variante de l'invention, les silices présentent un rapport SBET/SCTAB compris entre 1,0 et 1,2, c'est-à-dire que les silices présentent une faible microporosité.According to a variant of the invention, the silicas have an S BET / S CTAB ratio of between 1.0 and 1.2, that is to say that the silicas have a low microporosity.

    Selon une autre variante de l'invention, les silice présentent un rapport SBET/SCTAB supérieur à 1,2, par exemple compris entre 1,21 et 1,4, c'est-à-dire que les silices présentent une microporosité relativement élevée. According to another variant of the invention, the silica has an S BET / S CTAB ratio greater than 1.2, for example between 1.21 and 1.4, that is to say that the silicas have a microporosity relatively high.

    Les silices selon l'invention possèdent une prise d'huile DOP généralement comprise entre 150 et 400 ml/100 g, plus particulièrement entre 180 et 350 ml/100 g, par exemple entre 200 et 310 ml/100 g.The silicas according to the invention generally have a DOP oil intake between 150 and 400 ml / 100 g, more particularly between 180 and 350 ml / 100 g, for example between 200 and 310 ml / 100 g.

    Les silices selon l'invention se présentent sous forme de poudre, de billes sensiblement sphériques ou, éventuellement, de granulés et sont notamment caractérisées par le fait que, tout en ayant une taille relativement élevée, elles présentent une aptitude à la désagglomération et à la dispersion tout à fait remarquable et de bonnes propriétés renforçantes. Elles présentent ainsi une aptitude à la désagglomération et à la dispersion avantageusement supérieure, à surface spécifique identique ou proche et à taille identique ou proche, à celle des silices de l'art antérieur.The silicas according to the invention are in the form of powder, substantially spherical or possibly granular balls and are in particular characterized by the fact that, while having a relatively small size high, they have an ability to disaggregate and disperse quite remarkable and good reinforcing properties. They present thus an aptitude for deagglomeration and dispersion advantageously larger, with identical or similar specific surface and identical size or close to that of the silicas of the prior art.

    Les poudres de silice selon l'invention présentent une taille moyenne supérieure à 15 µm, en particulier comprise entre 20 et 150 µm, par exemple entre 30 et 100 µm.The silica powders according to the invention have a average size greater than 15 µm, in particular between 20 and 150 µm, for example between 30 and 100 µm.

    La densité de remplissage à l'état tassé (DRT) desdites poudres est, en général, d'au moins 0,17, et, par exemple, comprise entre 0,2 et 0,3.The packed filling density (DRT) of said powders is, in general, at least 0.17, and, for example, between 0.2 and 0.3.

    Lesdites poudres présentent généralement un volume poreux total d'au moins 2,5 cm3/g, et, plus particulièrement, compris entre 3 et 5 cm3/g.Said powders generally have a total pore volume of at least 2.5 cm 3 / g, and more particularly between 3 and 5 cm 3 / g.

    Elles permettent d'obtenir un très bon compromis mise en oeuvre/propriétés mécaniques finales à l'état vulcanisé.They make it possible to obtain a very good compromise between implementation and properties. final mechanical in vulcanized state.

    Elles constituent enfin des précurseurs privilégiés pour la synthèse de granulés tels que décrits plus loin.Finally, they constitute privileged precursors for the synthesis of granules as described below.

    Les billes sensiblement sphériques selon l'invention présentent une taille moyenne d'au moins 80 µm.The substantially spherical balls according to the invention have an average size of at least 80 µm.

    Selon certaines variantes de l'invention, cette taille moyenne des billes est d'au moins 100 µm, par exemple d'au moins 150 µm ; elle est généralement d'au plus 300 µm et se situe de préférence entre 100 et 270 µm. Cette taille moyenne est déterminée selon la norme NF X 11507 (décembre 1970) par tamisage à sec et détermination du diamètre correspondant à un refus cumulé de 50 %.According to certain variants of the invention, this average size of the beads is at least 100 µm, for example at least 150 µm; she is usually at least plus 300 µm and is preferably between 100 and 270 µm. This average size is determined according to standard NF X 11507 (December 1970) by dry sieving and determination of the diameter corresponding to a cumulative refusal of 50%.

    La densité de remplissage à l'état tassé (DRT) desdites billes est, en général, d'au moins 0,17, et, par exemple, comprise entre 0,2 et 0,32.The packed filling density (DRT) of said balls is, in general, at least 0.17, and, for example, between 0.2 and 0.32.

    Elles présentent généralement un volume poreux total d'au moins 2,5 cm3/g, et plus particulièrement, compris entre 3 et 5 cm3/g.They generally have a total pore volume of at least 2.5 cm 3 / g, and more particularly, between 3 and 5 cm 3 / g.

    Comme indiqué ci-avant, une telle silice sous forme de billes sensiblement sphériques, avantageusement pleines, homogènes, peu poussièrantes et de bonne coulabilité, présente une bonne aptitude à la désagglomération et à la dispersion. En outre, elle présente de bonnes propriétés renforçantes. Une telle silice constitue également un précurseur privilégié pour la synthèse des poudres et des granulés selon l'invention.As indicated above, such a silica in the form of beads substantially spherical, advantageously solid, homogeneous, little dusty and of good flowability, has a good ability to disaggregate and dispersion. In addition, it has good reinforcing properties. Such a silica also constitutes a privileged precursor for the synthesis of powders and granules according to the invention.

    Ces billes de manière avantageuse, présentent un diamètre médian (50), après désagglomération aux ultra-sons, inférieur à 3 µm et un facteur de désagglomération aux ultra-sons (FD) supérieur à 8 ml, par exemple à 12 ml.These beads advantageously have a median diameter ( 50 ), after deagglomeration with ultrasound, less than 3 μm and a deagglomeration factor with ultrasound (F D ) greater than 8 ml, for example 12 ml.

    Les dimensions des granulés selon l'invention sont d'au moins 1 mm, en particulier comprises entre 1 et 10 mm, selon l'axe de leur plus grande dimension (longueur).The dimensions of the granules according to the invention are at least minus 1 mm, in particular between 1 and 10 mm, along the axis of their plus large dimension (length).

    Lesdits granulés peuvent se présenter sous des formes les plus diverses. A titre d'exemple, on peut notamment citer les formes sphérique, cylindrique, parallélépipédique, de pastille, de plaquette, de boulette, d'extrudé à section circulaire ou polylobée.Said granules can be in the most diverse forms. AT By way of example, mention may in particular be made of spherical, cylindrical shapes, rectangular, pellet, wafer, dumpling, section extruded circular or multi-lobed.

    La densité de remplissage à l'état tassé (DRT) desdits granulés est en général d'au moins 0,27 et peut aller jusqu'à 0,37.The packed filling density (DRT) of said granules is in general at least 0.27 and can be up to 0.37.

    Ils présentent généralement un volume poreux total d'au moins 1 cm3/g, et, plus particulièrement, entre 1,5 et 2 cm3/g.They generally have a total pore volume of at least 1 cm 3 / g, and, more particularly, between 1.5 and 2 cm 3 / g.

    Les silices selon l'invention sont de préférence préparées par un procédé du type comprenant la réaction d'un silicate de métal alcalin M avec un agent acidifiant ce par quoi l'on obtient une suspension de silice précipitée, puis la séparation et le séchage de cette suspension, ledit procédé étant caractérisé en ce qu'on réalise la précipitation de la manière suivante :

  • (i) on forme un pied de cuve initial comportant une partie de la quantité totale du silicate de métal alcalin M engagé dans la réaction, la concentration en silicate exprimée en SiO2 dans ledit pied de cuve étant d'au plus 11 g/l,
  • (ii) on ajoute l'agent acidifiant audit pied de cuve initial jusqu'à ce qu'au moins 50 % de la quantité de M2O présente dans ledit pied de cuve initial soient neutralisés,
  • (iii) on ajoute au milieu réactionnel simultanément de l'agent acidifiant et la quantité restante de silicate de métal alcalin telle que le taux de consolidation, c'est-à-dire le rapport quantité de silicate ajoutée (exprimée en SiO2)/quantité de silicate présente dans le pied de cuve initial (exprimée en SiO2) soit compris entre 12 et 100.
    • The silicas according to the invention are preferably prepared by a process of the type comprising the reaction of an alkali metal silicate M with an acidifying agent whereby a suspension of precipitated silica is obtained, then the separation and drying of this suspension, said process being characterized in that precipitation is carried out as follows:
  • (i) forming an initial base stock comprising part of the total amount of the alkali metal silicate M used in the reaction, the silicate concentration expressed as SiO 2 in said base stock being at most 11 g / l ,
  • (ii) adding the acidifying agent to said initial base stock until at least 50% of the amount of M 2 O present in said initial base stock is neutralized,
  • (iii) acidifying agent and the remaining quantity of alkali metal silicate are added to the reaction medium simultaneously, such as the degree of consolidation, that is to say the ratio of quantity of silicate added (expressed as SiO 2 ) / quantity of silicate present in the initial base stock (expressed as SiO 2 ) is between 12 and 100.

    • Il a été ainsi trouvé qu'une concentration très faible en silicate exprimée en SiO2 dans le pied de cuve initial ainsi qu'un taux de consolidation approprié lors de l'étape d'addition simultané constituaient des conditions importantes pour conférer aux produits obtenus leurs excellentes propriétés. It was thus found that a very low concentration of silicate expressed as SiO 2 in the initial base stock as well as an appropriate consolidation rate during the simultaneous addition step constituted important conditions for conferring on the products obtained their excellent properties.

    Il est à noter, d'une manière générale, que le procédé concerné est un procédé de synthèse de silice de précipitation, c'est-à-dire que l'on fait agir un agent acidifiant sur un silicate de métal alcalin M.It should be noted, in general, that the process concerned is a precipitation silica synthesis process, that is to say that a acidifying agent on an alkali metal silicate M.

    Le choix de l'agent acidifiant et du silicate se fait d'une manière bien connue en soi. On peut rappeler qu'on utilise généralement comme agent acidifiant un acide minéral fort tel que l'acide sulfurique, l'acide nitrique ou l'acide chlorhydrique, ou un acide organique tel que l'acide acétique, l'acide formique ou l'acide carbonique.The choice of acidifying agent and silicate is made in a well known manner in itself. It may be recalled that a acidifying agent is generally used strong mineral acid such as sulfuric acid, nitric acid or acid hydrochloric acid, or an organic acid such as acetic acid, formic acid or carbonic acid.

    On peut par ailleurs utiliser en tant que silicate toute forme courante de silicates tels que métasilicates, disilicates et avantageusement un silicate de métal alcalin M dans lequel M est le sodium ou le potassium.It is also possible to use as silicate any common form of silicates such as metasilicates, disilicates and advantageously a silicate of alkali metal M in which M is sodium or potassium.

    De manière générale, on emploie, comme agent acidifiant, l'acide sulfurique, et, comme silicate, le silicate de sodium.Generally, as acidifying agent, acid is used sulfuric, and, as silicate, sodium silicate.

    Dans le cas où l'on utilise le silicate de sodium, celui-ci présente, en général, un rapport molaire SiO2/Na2O compris entre 2 et 4, plus particulièrement entre 3,0 et 3,7.In the case where sodium silicate is used, the latter generally has a SiO 2 / Na 2 O molar ratio of between 2 and 4, more particularly between 3.0 and 3.7.

    En ce qui concerne plus particulièrement le procédé préféré de préparation des silices de l'invention, la précipitation se fait d'une manière spécifique selon les étapes suivantes.With particular regard to the preferred method of preparation of the silicas of the invention, the precipitation takes place in a specific manner according to the following steps.

    On forme tout d'abord un pied de cuve qui comprend du silicate. La quantité de silicate présente dans ce pied de cuve initial ne représente avantageusement qu'une partie de la quantité totale de silicate engagée dans la réaction.First of all, a base stock is formed which comprises silicate. The amount of silicate present in this initial base stock does not advantageously represent only part of the total amount of silicate involved in the reaction.

    Selon une caractéristique essentielle du procédé de préparation selon l'invention, la concentration en silicate dans le pied de cuve initial est d'au plus 11 g/l et, éventuellement, d'au plus 8 g/l.According to an essential characteristic of the preparation process according to the invention, the silicate concentration in the initial base stock is not more than 11 g / l and, possibly not more than 8 g / l.

    Les conditions imposées à la concentration en silicate dans le pied de cuve initial conditionnent en partie les caractéristiques des silices obtenues.The conditions imposed on the silicate concentration in the base stock initial condition in part the characteristics of the silicas obtained.

    Le pied de cuve initial peut comprendre un électrolyte. Néanmoins, de préférence, aucun électrolyte n'est utilisé au cours du procédé de préparation selon l'invention ; en particulier, de manière préférée, le pied de cuve initial ne comprend pas d'électrolyte.The initial base stock may include an electrolyte. Nevertheless, preferably no electrolyte is used during the preparation process according to the invention; in particular, preferably, the initial base stock does not includes no electrolyte.

    Le terme électrolyte s'entend ici dans son acceptation normale, c'est-à-dire qu'il signifie toute substance ionique ou moléculaire qui, lorsqu'elle est en solution, se décompose ou se dissocie pour former des ions ou des particules chargées. On peut citer comme électrolyte un sel du groupe des sels des métaux alcalins et alcalino-terreux, notamment le sel du métal de silicate de départ et de l'agent acidifiant, par exemple le sulfate de sodium dans le cas de la réaction d'un silicate de sodium avec l'acide sulfurique.The term electrolyte is understood here in its normal acceptance, that is to say that it means any ionic or molecular substance which, when in solution, decomposes or dissociates to form ions or particles loaded. Mention may be made, as electrolyte, of a salt from the group of metal salts alkaline and alkaline earth metals, especially the salt of the starting silicate metal and the acidifying agent, for example sodium sulfate in the case of the reaction of a sodium silicate with sulfuric acid.

    La deuxième étape consiste à ajouter l'agent acidifiant dans le pied de cuve de composition décrite plus haut.The second step is to add the acidifying agent to the base. of composition described above.

    Ainsi, dans cette deuxième étape, on ajoute l'agent acidifiant audit pied de cuve initial jusqu'à ce qu'au moins 50 % de la quantité de M2O présente dans ledit pied de cuve initial soient neutralisés.Thus, in this second step, the acidifying agent is added to said initial base stock until at least 50% of the amount of M 2 O present in said initial base stock is neutralized.

    De manière préférée, dans cette deuxième étape, on ajoute l'agent acidifiant audit pied de cuve initial jusqu'à ce que 50 à 99 % de la quantité de M2O présente dans ledit pied de cuve initial soient neutralisés.Preferably, in this second step, the acidifying agent is added to said initial base stock until 50 to 99% of the amount of M 2 O present in said initial base stock is neutralized.

    L'agent acidifiant peut être dilué ou concentré ; sa normalité peut être comprise entre 0,4 et 36 N, par exemple entre 0,6 et 1,5 N.The acidifying agent can be diluted or concentrated; his normality can be between 0.4 and 36 N, for example between 0.6 and 1.5 N.

    En particulier, dans le cas où l'agent acidifiant est l'acide sulfurique, sa concentration est de préférence comprise entre 40 et 180 g/l, par exemple entre 60 et 130 g/l.In particular, in the case where the acidifying agent is sulfuric acid, its concentration is preferably between 40 and 180 g / l, for example between 60 and 130 g / l.

    Une fois qu'est atteinte la valeur souhaitée de quantité de M2O neutralisé, on procède alors à une addition simultanée (étape (iii)) d'agent acidifiant et d'une quantité de silicate de métal alcalin M telle que le taux de consolidation, c'est-à-dire le rapport quantité de silice ajoutée/quantité de silice présente dans le pied de cuve initial soit compris entre 12 et 100, de préférence entre 12 et 50, en particulier entre 13 et 40.Once the desired value of quantity of neutralized M 2 O has been reached, a simultaneous addition (step (iii)) of acidifying agent and of an amount of alkali metal silicate M such as the rate of consolidation, that is to say the ratio of quantity of silica added / quantity of silica present in the initial base stock is between 12 and 100, preferably between 12 and 50, in particular between 13 and 40.

    De manière préférée, pendant toute l'étape (iii), la quantité d'agent acidifiant ajoutée est telle que 80 à 99 %, par exemple 85 à 97 %, de la quantité de M2O ajoutée soient neutralisés.Preferably, during all of step (iii), the amount of acidifying agent added is such that 80 to 99%, for example 85 to 97%, of the amount of M 2 O added is neutralized.

    Dans l'étape (iii), il est possible de procéder à l'addition simultanée d'agent acidifiant et de silicate à un premier palier de pH du milieu réactionnel, pH1, puis à un second palier de pH du milieu réactionnel, pH2, tel que 7 < pH2 < pH1 < 9.In step (iii), it is possible to carry out the simultaneous addition of acidifying agent and silicate to a first level of pH of the reaction medium, pH 1 , then to a second level of pH of the reaction medium, pH 2 , such as 7 <pH 2 <pH 1 <9.

    L'agent acidifiant utilisé lors de l'étape (iii) peut être dilué ou concentré ; sa normalité peut être comprise entre 0,4 et 36 N, par exemple entre 0,6 et 1,5 N.The acidifying agent used during step (iii) can be diluted or concentrated; her normality can be between 0.4 and 36 N, for example between 0.6 and 1.5 N.

    En particulier, dans le cas où cet agent acidifiant est l'acide sulfurique, sa concentration est de préférence comprise entre 40 et 180 g/l, par exemple entre 60 et 130 g/l.In particular, in the case where this acidifying agent is sulfuric acid, its concentration is preferably between 40 and 180 g / l, for example between 60 and 130 g / l.

    En général, le silicate de métal alcalin M ajouté lors de l'étape (iii) présente une concentration exprimée en silice comprise entre 40 et 330 g/l, par exemple entre 60 et 250 g/l.In general, the alkali metal silicate M added during step (iii) has a concentration expressed as silica of between 40 and 330 g / l, for example between 60 and 250 g / l.

    La réaction de précipitation proprement dite est terminée lorsque l'on a ajouté toute la quantité restante de silicate. The actual precipitation reaction is complete when added all the remaining amount of silicate.

    Il est avantageux d'effectuer, notamment après l'addition simultanée précitée, un mûrissement du milieu réactionnel, ce mûrissement pouvant par exemple durer de 1 à 60 minutes, en particulier de 5 à 30 minutes.It is advantageous to perform, especially after the simultaneous addition mentioned above, a ripening of the reaction medium, this ripening possibly by example last from 1 to 60 minutes, in particular from 5 to 30 minutes.

    Il est enfin souhaitable, après la précipitation, dans une étape ultérieure, notamment avant le mûrissement éventuel, d'ajouter au milieu réactionnel une quantité supplémentaire d'agent acidifiant. Cette addition se fait généralement jusqu'à l'obtention d'une valeur du pH du milieu réactionnel comprise entre 3 et 6,5, de préférence entre 4 et 5,5. Elle permet notamment de neutraliser toute la quantité de M2O ajoutée lors de l'étape (iii) et de régler le pH de la silice finale à la valeur désirée pour une application donnée.Finally, it is desirable, after precipitation, in a subsequent step, in particular before possible ripening, to add to the reaction medium an additional amount of acidifying agent. This addition is generally carried out until a pH value of the reaction medium of between 3 and 6.5, preferably between 4 and 5.5, is obtained. In particular, it makes it possible to neutralize the entire quantity of M 2 O added during step (iii) and to adjust the pH of the final silica to the desired value for a given application.

    L'agent acidifiant utilisée lors de cette addition est généralement identique à celui employé lors de l'étape (iii) du procédé de préparation selon l'invention.The acidifying agent used during this addition is generally identical to that used during step (iii) of the preparation process according to the invention.

    La température du milieu réactionnel est habituellement comprise entre 60 et 98 °C.The temperature of the reaction medium is usually between 60 and 98 ° C.

    De préférence, l'addition d'agent acidifiant lors de l'étape (ii) s'effectue dans un pied de cuve initial dont la température est comprise entre 60 et 96 °C.Preferably, the addition of acidifying agent during step (ii) is carried out in an initial base stock whose temperature is between 60 and 96 ° C.

    Selon une variante de l'invention, la réaction est effectuée à une température constante comprise entre 75 et 96 °C. Selon une autre variante de l'invention, la température de fin de réaction est plus élevée que la température de début de réaction : ainsi, on maintient la température au début de la réaction de préférence entre 70 et 96 °C, puis on augmente la température en cours de réaction en quelques minutes, de préférence jusqu'à une valeur comprise entre 80 et 98 °C, valeur à laquelle elle est maintenue jusqu'à la fin de la réaction.According to a variant of the invention, the reaction is carried out at a constant temperature between 75 and 96 ° C. According to another variant of the invention, the end of reaction temperature is higher than the temperature start of reaction: thus, the temperature is maintained at the start of the reaction preferably between 70 and 96 ° C, then the temperature is increased during reaction in a few minutes, preferably up to a value between 80 and 98 ° C, value at which it is maintained until the end of the reaction.

    On obtient, à l'issue des opérations qui viennent d'être décrites, une bouillie de silice qui est ensuite séparée (séparation liquide-solide). Cette séparation consiste généralement en une filtration, suivie d'un lavage si nécessaire. La filtration peut se faire selon toute méthode convenable, par exemple par filtre presse ou filtre à bande ou filtre rotatif sous vide.At the end of the operations which have just been described, a slurry is obtained. silica which is then separated (liquid-solid separation). This separation generally consists of filtration, followed by washing if necessary. The filtration can be done by any suitable method, for example by filter press or belt filter or rotary vacuum filter.

    La suspension de silice précipitée ainsi récupérée (gâteau de filtration) est ensuite séchée.The precipitated silica suspension thus recovered (filtration cake) is then dried.

    Ce séchage peut se faire selon tout moyen connu en soi.This drying can be done by any means known per se.

    De préférence, le séchage se fait par atomisation.Preferably, the drying is carried out by atomization.

    A cet effet, on peut utiliser tout type d'atomiseur convenable, notamment des atomiseurs à turbines, à buses, à pression liquide ou à deux fluides.For this purpose, any suitable type of atomizer can be used, in particular atomizers with turbines, nozzles, liquid pressure or two fluids.

    Selon une variante du procédé de préparation, la suspension à sécher présente un taux de matière sèche supérieur à 18 % en poids, de préférence supérieur à 20 % en poids. Le séchage est alors généralement effectué au moyen d'un atomiseur à turbines ou, de préférence, à buses. According to a variant of the preparation process, the suspension to be dried has a dry matter content greater than 18% by weight, preferably more than 20% by weight. The drying is then generally carried out at by means of a turbine atomizer or, preferably, nozzles.

    La silice précipitée susceptible d'être obtenue selon cette variante du procédé se présente généralement sous forme de billes sensiblement sphériques, de préférence d'une taille moyenne d'au moins 80 µm.The precipitated silica capable of being obtained according to this variant of the process generally takes the form of beads substantially spherical, preferably with an average size of at least 80 µm.

    Cette teneur en matière sèche peut être obtenue directement à la filtration en utilisant un filtre convenable donnant un gâteau de filtration à la bonne teneur. Une autre méthode consiste, après la filtration, à une étape ultérieure du procédé, à rajouter au gâteau de la matière sèche, par exemple de la silice sous forme pulvérulente, de manière à obtenir la teneur nécessaire.This dry matter content can be obtained directly by filtration using a suitable filter giving a filter cake with the right content. Another method consists, after filtration, at a later stage of the process, adding dry matter, for example silica under the cake pulverulent form, so as to obtain the necessary content.

    Il y a lieu de noter que, comme cela est bien connu, le gâteau ainsi obtenu n'est pas, en général, dans des conditions permettant une atomisation notamment à cause de sa viscosité trop élevée.It should be noted that, as is well known, the cake thus obtained is not, in general, in conditions allowing atomization especially because of its too high viscosity.

    D'une manière connue en soi, on soumet alors le gâteau à une opération de délitage. Cette opération peut se faire par passage du gâteau dans un broyeur de type colloïdal ou à bille. Par ailleurs, pour abaisser la viscosité de la suspension à atomiser, il est possible d'ajouter de l'aluminium notamment sous forme d'aluminate de sodium au cours du procédé comme décrit dans la demande de brevet FR-A-2536380 dont l'enseignement est incorporé ici. Cette addition peut se faire en particulier au moment même du délitage.In a manner known per se, the cake is then subjected to an operation of disintegration. This operation can be done by passing the cake through a grinder of colloidal or ball type. Furthermore, to lower the viscosity of the suspension to atomize, it is possible to add aluminum especially in the form sodium aluminate during the process as described in the application for Patent FR-A-2536380, the teaching of which is incorporated here. This addition can be done in particular at the time of the disintegration.

    A l'issue du séchage, on peut procéder à une étape de broyage sur le produit récupéré, notamment sur le produit obtenu par séchage de la suspension présentant un taux de matière sèche supérieur à 18 % en poids. La silice précipitée qui est alors susceptible d'être obtenue se présente généralement sous forme d'une poudre, de préférence de taille moyenne d'au moins 15 µm, en particulier comprise entre 20 et 150 µm, par exemple entre 30 et 100 µm.After drying, a grinding step can be carried out on the recovered product, in particular on the product obtained by drying the suspension having a dry matter content greater than 18% by weight. Silica precipitate which is then likely to be obtained generally occurs in the form of a powder, preferably of average size of at least 15 μm, in particular between 20 and 150 μm, for example between 30 and 100 μm.

    Les produits broyés à la granulométrie désirée peuvent être séparés des éventuels produits non conformes au moyen par exemple de tamis vibreurs présentant des tailles de maille appropriées, et les produits non conformes ainsi récupérés être renvoyés au broyage.Products ground to the desired particle size can be separated from any non-conforming products using, for example, vibrating screens with appropriate mesh sizes, and non-conforming products as well recovered be returned to grinding.

    De même, selon une autre variante du procédé de préparation, la suspension à sécher présente un taux de matière sèche inférieur à 18 % en poids. Le séchage est alors en général effectué au moyen d'un atomiseur à turbines ou à buses. La silice précipitée qui est alors susceptible d'être obtenue selon cette variante de l'invention se présente généralement sous la forme d'une poudre, de préférence de taille moyenne d'au moins 15 µm, en particulier comprise entre 20 et 150 µm, par exemple entre 30 et 100 µm.Similarly, according to another variant of the preparation process, the suspension to be dried has a dry matter content of less than 18% in weight. The drying is then generally carried out by means of an atomizer with turbines or nozzles. Precipitated silica which can then be obtained according to this variant of the invention is generally in the form of a powder, preferably of average size of at least 15 μm, in particular between 20 and 150 µm, for example between 30 and 100 µm.

    Une opération de délitage peut être également ici réalisée. A disintegration operation can also be carried out here.

    Enfin, le produit séché (notamment à partir d'une suspension ayant un taux de matière sèche inférieur à 18 % en poids) ou broyé peut, selon une autre variante du procédé de l'invention, être soumis à une étape d'agglomération.Finally, the dried product (in particular from a suspension having a rate dry matter less than 18% by weight) or ground may, according to another variant of the process of the invention, be subjected to an agglomeration step.

    On entend ici par agglomération tout procédé qui permet de lier entre eux des objets finement divisés pour les amener sous la forme d'objets de plus grande taille et résistant mécaniquement.By agglomeration is meant here any process which makes it possible to link them finely divided objects to bring them in the form of more objects large size and mechanically resistant.

    Ces procédés sont notamment la compression directe, la granulation voie humide (c'est-à-dire avec utilisation d'un liant tel que eau, slurry de silice, ...), l'extrusion et, de préférence, le compactage à sec.These processes include direct compression, track granulation wet (i.e. with the use of a binder such as water, silica slurry, ...), extrusion and, preferably, dry compaction.

    Lorsque l'on met en oeuvre cette dernière technique, il peut s'avérer avantageux, avant de procéder au compactage, de désaérer (opération aussi appelée pré-densification ou dégazage) les produits pulvérulents de manière à éliminer l'air inclus dans ceux-ci et assurer un compactage plus régulier.When implementing this latter technique, it may be advantageous, before proceeding to compaction, to deaerate (operation also called pre-densification or degassing) the powdery products so as to eliminate the air included in them and ensure more regular compaction.

    La silice précipitée susceptible d'être obtenue selon cette variante du procédé se présente avantageusement sous la forme de granulés, de préférence de taille d'au moins 1 mm, en particulier comprise entre 1 et 10 mm.The precipitated silica capable of being obtained according to this variant of the process is advantageously in the form of granules, preferably at least 1 mm in size, in particular between 1 and 10 mm.

    A l'issue de l'étape d'agglomération, les produits peuvent être calibrés à une taille désirée, par exemple par tamisage, puis conditionnés pour leur utilisation future.At the end of the agglomeration stage, the products can be calibrated to a desired size, for example by sieving, then packaged for use future.

    Les poudres, de même que les billes, de silice précipitée obtenues par le procédé de l'invention offrent ainsi l'avantage, entre autre, d'accéder de manière simple, efficace et économique à des granulés tels que précités, notamment par des opérations classiques de mise en forme, telles que par exemple une granulation ou un compactage, sans que ces dernières n'entraínent de dégradations susceptibles de masquer, voire annihiler, les propriétés renforçantes intrinsèques attachées à ces poudres, comme cela peut être le cas dans l'art antérieur en mettant en oeuvre des poudres classiques.The powders, as well as the beads, of precipitated silica obtained by the method of the invention thus offer the advantage, among other things, of accessing simple, effective and economical with granules as mentioned above, in particular by conventional shaping operations, such as for example a granulation or compaction, without the latter causing degradations likely to mask or even annihilate the properties intrinsic reinforcers attached to these powders, as may be the case in the prior art by using conventional powders.

    Les silices selon l'invention trouvent une application particulièrement intéressante dans le renforcement des élastomères, naturels ou synthétiques, et notamment des pneumatiques. Elles confèrent à ces élastomères une amélioration significative de leurs propriétés mécaniques, comme l'allongement à la rupture, la résistance à la rupture et au déchirement, tout en leur procurant des propriétés rhéologiques très satisfaisantes.The silicas according to the invention find a particularly application interesting in the reinforcement of elastomers, natural or synthetic, and including tires. They give these elastomers a significant improvement in their mechanical properties, such as elongation at breaking, breaking and tearing resistance, while providing them with very satisfactory rheological properties.

    Les exemples suivants illustrent l'invention sans toutefois en limiter la portée. The following examples illustrate the invention without, however, limiting its scope.

    EXEMPLE 1EXAMPLE 1

    Dans un réacteur en acier inoxydable muni d'un système d'agitation par hélices et d'un chauffage par double enveloppe, on introduit 662 litres d'une solution de silicate de sodium (de rapport molaire SiO2/Na2O égal à 3,4) ayant une concentration exprimée en silice de 10 g/l.662 liters of a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.

    La concentration en silicate exprimée en SiO2 dans le pied de cuve initial est donc de 10 g/l. La solution est alors portée à une température de 85 °C tout en la maintenant sous agitation. L'ensemble de la réaction est effectué à 85 °C. On y introduit ensuite, pendant 3 mn et 20 s, une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn ; à l'issue de cette addition, le taux de neutralisation du pied de cuve est de 85 %, c'est-à-dire que 85 % de la quantité de Na2O présente dans le pied de cuve initial sont neutralisés.The silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l. The solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C. Then there is introduced, for 3 min and 20 s, a sulfuric acid solution, with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.

    On introduit ensuite simultanément, pendant 70 mn, dans le milieu réactionnel :

    • une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn, et
    • une solution de silicate de sodium, de concentration exprimée en silice égale à 130 g/l, à un débit de 14,2 l/mn.
    Then introduced simultaneously, for 70 min, into the reaction medium:
    • a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 10.2 l / min, and
    • a sodium silicate solution, concentration expressed as silica equal to 130 g / l, at a flow rate of 14.2 l / min.

    Lors de cette addition simultanée, le taux de neutralisation instantané est de 92 %, c'est-à-dire que 92 % de la quantité de Na2O ajoutée (par mn) sont neutralisés.During this simultaneous addition, the instantaneous neutralization rate is 92%, that is to say that 92% of the amount of Na 2 O added (per minute) are neutralized.

    Le taux de consolidation, à l'issue de cette addition simultanée, est égal à 19,5.The consolidation rate, after this simultaneous addition, is equal to 19.5.

    Après introduction de la totalité du silicate, on continue à introduire la solution d'acide sulfurique, au même débit, et ceci pendant 10 mn. Cette introduction complémentaire d'acide amène alors le pH du milieu réactionnel à une valeur ègale à 4,5.After introduction of all of the silicate, the introduction of the sulfuric acid solution, at the same flow rate, for 10 min. This additional introduction of acid then brings the pH of the reaction medium to a value equal to 4.5.

    On obtient ainsi une bouillie de silice précipitée qui est filtrée et lavée au moyen d'un filtre rotatif sous vide de telle sorte que l'on récupère finalement un gâteau de silice dont la perte au feu est de 87 % (donc un taux de matière sèche de 13 % en poids).A precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).

    Ce gâteau est ensuite fluidifié par simple action mécanique. Après cette opération de délitage, la bouillie résultante est atomisée au moyen d'un atomiseur à turbines.This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.

    Les caractéristiques de la silice P1 sous forme de poudre (conforme à l'invention) sont alors les suivantes :

    • surface spécifique CTAB   125 m2/g
    • surface spécifique BET   164 m2/g
    • volume poreux V1 représenté
      par les pores de d ≤ 400 Å   0,58 cm3/g
    • volume poreux V2 représenté
      par les pores 175 Å ≤ d ≤ 275 Å   0,14 cm3/g
    • rapport V2/V1   24 %
    • taille moyenne des particules   60 µm
    The characteristics of the silica P1 in powder form (according to the invention) are then as follows:
    • specific surface CTAB 125 m 2 / g
    • BET specific surface 164 m 2 / g
    • pore volume V1 shown
      through pores of d ≤ 400 Å 0.58 cm 3 / g
    • pore volume V2 shown
      through pores 175 Å ≤ d ≤ 275 Å 0.14 cm 3 / g
    • V2 / V1 ratio 24%
    • average particle size 60 µm

    On soumet la silice P1 au test de désagglomération tel que défini précédemment dans la description.The silica P1 is subjected to the deagglomeration test as defined earlier in the description.

    Après désagglomération aux ultra-sons, elle présente un diamètre médian (⊘50) de 2,35 µm et un facteur de désagglomération aux ultra-sons (FD) de 5,2 ml.After ultrasonic deagglomeration, it has a median diameter (⊘ 50 ) of 2.35 µm and an ultrasonic deagglomeration factor (F D ) of 5.2 ml.

    EXEMPLE 2EXAMPLE 2

    On procède comme dans l'exemple 1, excepté au niveau de l'addition simultanée des solutions d'acide sulfurique et de silicate de sodium. Ainsi :The procedure is as in Example 1, except for the addition simultaneous solutions of sulfuric acid and sodium silicate. So :

    Dans un réacteur en acier inoxydable muni d'un système d'agitation par hélices et d'un chauffage par double enveloppe, on introduit 662 litres d'une solution de silicate de sodium (de rapport molaire SiO2/Na2O égal à 3,4) ayant une concentration exprimée en silice de 10 g/l.662 liters of a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.

    La concentration en silicate exprimée en SiO2 dans le pied de cuve initial est donc de 10 g/l. La solution est alors portée à une température de 85 °C tout en la maintenant sous agitation. L'ensemble de la réaction est effectué à 85 °C. On y introduit ensuite, pendant 3 mn et 20 s, une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn ; à l'issue de cette addition, le taux de neutralisation du pied de cuve est de 85 %, c'est-à-dire que 85 % de la quantité de Na2O présente dans le pied de cuve initial sont neutralisés.The silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l. The solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C. Then there is introduced, for 3 min and 20 s, a sulfuric acid solution, with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.

    On introduit ensuite simultanément, pendant 70 mn, dans le milieu réactionnel :

    • une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn, et
    • une solution de silicate de sodium, de concentration exprimée en silice égale à 230 g/l, à un débit de 7,9 l/mn.
    Then introduced simultaneously, for 70 min, into the reaction medium:
    • a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 10.2 l / min, and
    • a sodium silicate solution, concentration expressed as silica equal to 230 g / l, at a flow rate of 7.9 l / min.

    Lors de cette addition simultanée, le taux de neutralisation instantané est de 93 %, c'est-à-dire que 93 % de la quantité de Na2O ajoutée (par mn) sont neutralisés.During this simultaneous addition, the instantaneous neutralization rate is 93%, that is to say that 93% of the amount of Na 2 O added (per minute) are neutralized.

    Le taux de consolidation, à l'issue de cette addition simultanée, est égal à 19,2.The consolidation rate, after this simultaneous addition, is equal to 19.2.

    Après introduction de la totalité du silicate, on continue à introduire la solution d'acide sulfurique, au même débit, et ceci pendant 10 mn. Cette introduction complémentaire d'acide amène alors le pH du milieu réactionnel à une valeur ègale à 4,5.After introduction of all of the silicate, the introduction of the sulfuric acid solution, at the same flow rate, for 10 min. This additional introduction of acid then brings the pH of the reaction medium to a value equal to 4.5.

    On obtient ainsi une bouillie de silice précipitée qui est filtrée et lavée au moyen d'un filtre rotatif sous vide de telle sorte que l'on récupère finalement un gâteau de silice dont la perte au feu est de 87,1 % (donc un taux de matière sèche de 12,9 % en poids).A precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87.1% (therefore a material content 12.9% by weight).

    Ce gâteau est ensuite fluidifié par simple action mécanique. Après cette opération de délitage, la bouillie résultante est atomisée au moyen d'un atomiseur à turbines.This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.

    Les caractéristiques de la silice P2 sous forme de poudre (conforme à l'invention) sont alors les suivantes :

    • surface spécifique CTAB   100 m2/g
    • surface spécifique BET   138 m2/g
    • volume poreux V1 représenté
      par les pores de d < 400 Å   0,26 cm3/g
    • volume poreux V2 représenté
      par les pores 175 Å ≤ d ≤ 275 Å   0,07 cm3/g
    • rapport V2/V1   27 %
    • taille moyenne des particules   60 µm
    The characteristics of the silica P2 in powder form (according to the invention) are then as follows:
    • CTAB specific surface 100 m 2 / g
    • BET specific surface 138 m 2 / g
    • pore volume V1 shown
      through pores of d <400 Å 0.26 cm 3 / g
    • pore volume V2 shown
      through pores 175 Å ≤ d ≤ 275 Å 0.07 cm 3 / g
    • V2 / V1 ratio 27%
    • average particle size 60 µm

    On soumet la silice P2 au test de désagglomération tel que défini précédemment dans la description.The silica P2 is subjected to the deagglomeration test as defined earlier in the description.

    Après désagglomération aux ultra-sons, elle présente un diamètre médian (50) de 3,6 µm et un facteur de désagglomération aux ultra-sons (FD) de 3,5 ml.After ultrasonic deagglomeration, it has a median diameter ( 50 ) of 3.6 μm and an ultrasonic deagglomeration factor (F D ) of 3.5 ml.

    EXEMPLE 3EXAMPLE 3

    Dans un réacteur en acier inoxydable muni d'un système d'agitation par hélices et d'un chauffage par double enveloppe, on introduit 662 litres d'une solution de silicate de sodium (de rapport molaire SiO2/Na2O égal à 3,4) ayant une concentration exprimée en silice de 5 g/l.662 liters of a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 5 g / l.

    La concentration en silicate exprimée en SiO2 dans le pied de cuve initial est donc de 5 g/l. La solution est alors portée à une température de 85 °C tout en la maintenant sous agitation. L'ensemble de la réaction est effectué à 85 °C. On y introduit ensuite, pendant 1 mn et 40 s, une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn ; à l'issue de cette addition, le taux de neutralisation du pied de cuve est de 85 %, c'est-à-dire que 85 % de la quantité de Na2O présente dans le pied de cuve initial sont neutralisés.The silicate concentration expressed as SiO 2 in the initial base stock is therefore 5 g / l. The solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C. Then there is introduced, for 1 min and 40 s, a sulfuric acid solution, with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.

    On introduit ensuite simultanément, pendant 70 mn, dans le milieu réactionnel :

    • une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn, et
    • une solution de silicate de sodium, de concentration exprimée en silice égale à 130 g/l, à un débit de 14,2 l/mn.
    Then introduced simultaneously, for 70 min, into the reaction medium:
    • a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 10.2 l / min, and
    • a sodium silicate solution, concentration expressed as silica equal to 130 g / l, at a flow rate of 14.2 l / min.

    Lors de cette addition simultanée, le taux de neutralisation instantané est de 92 %, c'est-à-dire que 92 % de la quantité de Na2O ajoutée (par mn) sont neutralisés.During this simultaneous addition, the instantaneous neutralization rate is 92%, that is to say that 92% of the amount of Na 2 O added (per minute) are neutralized.

    Le taux de consolidation, à l'issue de cette addition simultanée, est égal à 39,0.The consolidation rate, after this simultaneous addition, is equal to 39.0.

    Après introduction de la totalité du silicate, on continue à introduire la solution d'acide sulfurique, au même débit, et ceci pendant 10 mn. Cette introduction complémentaire d'acide amène alors le pH du milieu réactionnel à une valeur ègale à 4,5.After introduction of all of the silicate, the introduction of the sulfuric acid solution, at the same flow rate, for 10 min. This additional introduction of acid then brings the pH of the reaction medium to a value equal to 4.5.

    On obtient ainsi une bouillie de silice précipitée qui est filtrée et lavée au moyen d'un filtre rotatif sous vide de telle sorte que l'on récupère finalement un gâteau de silice dont la perte au feu est de 87 % (donc un taux de matière sèche de 13 % en poids).A precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).

    Ce gâteau est ensuite fluidifié par simple action mécanique. Après cette opération de délitage, la bouillie résultante est atomisée au moyen d'un atomiseur à turbines.This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.

    Les caractéristiques de la silice P3 sous forme de poudre (conforme à l'invention) sont alors les suivantes :

    • surface spécifique CTAB   119 m2/g
    • surface spécifique BET   137 m2/g
    • volume poreux V1 représenté
      par les pores de d ≤ 400 Å   0,38 cm3/g
    • volume poreux V2 représenté
      par les pores 175 Å ≤ d ≤ 275 Å   0,10 cm3/g
    • rapport V2/V1   26 %
    • taille moyenne des particules   60 µm
    The characteristics of the silica P3 in powder form (according to the invention) are then as follows:
    • specific surface CTAB 119 m 2 / g
    • BET specific surface 137 m 2 / g
    • pore volume V1 shown
      through pores of d ≤ 400 Å 0.38 cm 3 / g
    • pore volume V2 shown
      through the pores 175 Å ≤ d ≤ 275 Å 0.10 cm 3 / g
    • V2 / V1 ratio 26%
    • average particle size 60 µm

    On soumet la silice P3 au test de désagglomération tel que défini précédemment dans la description.The silica P3 is subjected to the deagglomeration test as defined earlier in the description.

    Après désagglomération aux ultra-sons, elle présente un diamètre médian (Ø50) de 2,3 µm et un facteur de désagglomération aux ultra-sons (FD) de 5,0 ml.After ultrasonic deagglomeration, it has a median diameter (Ø 50 ) of 2.3 μm and an ultrasonic deagglomeration factor (F D ) of 5.0 ml.

    EXEMPLE 4EXAMPLE 4

    Dans un réacteur en acier inoxydable muni d'un système d'agitation par hélices et d'un chauffage par double enveloppe, on introduit 662 litres d'une solution de silicate de sodium (de rapport molaire SiO2/Na2O égal à 3,4) ayant une concentration exprimée en silice de 10 g/l.662 liters of a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.

    La concentration en silicate exprimée en SiO2 dans le pied de cuve initial est donc de 10 g/l. La solution est alors portée à une température de 85 °C tout en la maintenant sous agitation. On y introduit ensuite, pendant 3 mn et 20 s, une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn ; la température du milieu réactionnel est maintenue à 85 °C pendant l'addition de la solution d'acide sulfurique ; à l'issue de cette addition, le taux de neutralisation du pied de cuve est de 85 %, c'est-à-dire que 85 % de la quantité de Na2O présente dans le pied de cuve initial sont neutralisés.The silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l. The solution is then brought to a temperature of 85 ° C. while keeping it under stirring. Then there is introduced, for 3 min and 20 s, a sulfuric acid solution, with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; the temperature of the reaction medium is maintained at 85 ° C. during the addition of the sulfuric acid solution; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.

    On introduit ensuite simultanément, pendant 70 mn, dans le milieu réactionnel :

    • une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 9,9 l/mn, et
    • une solution de silicate de sodium, de concentration exprimée en silice égale à 130 g/l, à un débit de 14,2 l/mn.
    Then introduced simultaneously, for 70 min, into the reaction medium:
    • a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 9.9 l / min, and
    • a sodium silicate solution, concentration expressed as silica equal to 130 g / l, at a flow rate of 14.2 l / min.

    La température du milieu réactionnel est maintenue à 85 °C pendant les 50 premières minutes de l'addition simultanée ; elle est ensuite portée de 85 à 90 °C en 5 mn, puis maintenue à 90 °C jusqu'à la fin de la réaction.The temperature of the reaction medium is maintained at 85 ° C. for the 50 first minutes of simultaneous addition; it is then brought from 85 to 90 ° C in 5 min, then maintained at 90 ° C until the end of the reaction.

    Lors de cette addition simultanée, le taux de neutralisation instantané est de 90 %, c'est-à-dire que 90 % de la quantité de Na2O ajoutée (par mn) sont neutralisés. During this simultaneous addition, the instantaneous neutralization rate is 90%, that is to say that 90% of the amount of Na 2 O added (per minute) are neutralized.

    Le taux de consolidation, à l'issue de cette addition simultanée, est égal à 19,5.The consolidation rate, after this simultaneous addition, is equal to 19.5.

    Après introduction de la totalité du silicate, on continue à introduire la solution d'acide sulfurique, au même débit, et ceci pendant 10 mn. Cette introduction complémentaire d'acide amène alors le pH du milieu réactionnel à une valeur ègale à 4,5.After introduction of all of the silicate, the introduction of the sulfuric acid solution, at the same flow rate, for 10 min. This additional introduction of acid then brings the pH of the reaction medium to a value equal to 4.5.

    On laisse ensuite mûrir le milieu réactionnel pendant 10 mn (sous agitation, à 90 °C).The reaction medium is then left to mature for 10 min (with stirring, at 90 ° C).

    On obtient ainsi une bouillie de silice précipitée qui est filtrée et lavée au moyen d'un filtre rotatif sous vide de telle sorte que l'on récupère finalement un gâteau de silice dont la perte au feu est de 87 % (donc un taux de matière sèche de 13 % en poids).A precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).

    Ce gâteau est ensuite fluidifié par simple action mécanique. Après cette opération de délitage, la bouillie résultante est atomisée au moyen d'un atomiseur à turbines.This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.

    Les caractéristiques de la silice P4 sous forme de poudre (conforme à l'invention) sont alors les suivantes :

    • surface spécifique CTAB   109 m2/g
    • surface spécifique BET   136 m2/g
    • volume poreux V1 représenté
      par les pores de d ≤ 400 Å   0,38 cm3/g
    • volume poreux V2 représenté
      par les pores 175 Å ≤ d ≤ 275 Å   0,12 cm3/g
    • rapport V2/V1   32 %
    • taille moyenne des particules   60 µm
    The characteristics of the silica P4 in powder form (according to the invention) are then as follows:
    • specific surface CTAB 109 m 2 / g
    • BET specific surface area 136 m 2 / g
    • pore volume V1 shown
      through pores of d ≤ 400 Å 0.38 cm 3 / g
    • pore volume V2 shown
      through the pores 175 Å ≤ d ≤ 275 Å 0.12 cm 3 / g
    • V2 / V1 ratio 32%
    • average particle size 60 µm

    On soumet la silice P4 au test de désagglomération tel que défini précédemment dans la description.The silica P4 is subjected to the deagglomeration test as defined earlier in the description.

    Après désagglomération aux ultra-sons, elle présente un diamètre médian (⊘50) de 3,0 µm et un facteur de désagglomération aux ultra-sons (FD) de 4,0 ml.After ultrasonic deagglomeration, it has a median diameter (⊘ 50 ) of 3.0 µm and an ultrasonic deagglomeration factor (F D ) of 4.0 ml.

    EXEMPLE 5EXAMPLE 5

    On procède comme dans l'exemple 4, excepté au niveau de la température du milieu réactionnel. Ainsi : The procedure is as in Example 4, except for the temperature of the reaction medium. So :

    Dans un réacteur en acier inoxydable muni d'un système d'agitation par hélices et d'un chauffage par double enveloppe, on introduit 662 litres d'une solution de silicate de sodium (de rapport molaire SiO2/Na2O égal à 3,4) ayant une concentration exprimée en silice de 10 g/l.662 liters of a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3) are introduced into a stainless steel reactor fitted with a propeller stirring system and a jacket heating. , 4) having a concentration expressed as silica of 10 g / l.

    La concentration en silicate exprimée en SiO2 dans le pied de cuve initial est donc de 10 g/l. La solution est alors portée à une température de 80 °C tout en la maintenant sous agitation. On y introduit ensuite, pendant 3 mn et 20 s, une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 10,2 l/mn ; la température du milieu réactionnel est maintenue à 80 °C pendant l'addition de la solution d'acide sulfurique ; à l'issue de cette addition, le taux de neutralisation du pied de cuve est de 85 %, c'est-à-dire que 85 % de la quantité de Na2O présente dans le pied de cuve initial sont neutralisés.The silicate concentration expressed as SiO 2 in the initial base stock is therefore 10 g / l. The solution is then brought to a temperature of 80 ° C. while keeping it under stirring. Then there is introduced, for 3 min and 20 s, a sulfuric acid solution, with a concentration equal to 80 g / l, at a flow rate of 10.2 l / min; the temperature of the reaction medium is maintained at 80 ° C. during the addition of the sulfuric acid solution; at the end of this addition, the neutralization rate of the base stock is 85%, that is to say that 85% of the amount of Na 2 O present in the initial base stock is neutralized.

    On introduit ensuite simultanément, pendant 70 mn, dans le milieu réactionnel :

    • une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 9,9 l/mn, et
    • une solution de silicate de sodium, de concentration exprimée en silice égale à 130 g/l, à un débit de 14,2 l/mn.
    Then introduced simultaneously, for 70 min, into the reaction medium:
    • a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 9.9 l / min, and
    • a sodium silicate solution, concentration expressed as silica equal to 130 g / l, at a flow rate of 14.2 l / min.

    La température du milieu réactionnel est maintenue à 80 °C pendant les 50 premières minutes de l'addition simultanée ; elle est ensuite portée de 80 à 95 °C en 7 mn, puis maintenue à 95 °C jusqu'à la fin de la réaction.The temperature of the reaction medium is maintained at 80 ° C. for the 50 first minutes of simultaneous addition; it is then brought from 80 to 95 ° C in 7 min, then maintained at 95 ° C until the end of the reaction.

    Lors de cette addition simultanée, le taux de neutralisation instantané est de 90 %, c'est-à-dire que 90 % de la quantité de Na2O ajoutée (par mn) sont neutralisés.During this simultaneous addition, the instantaneous neutralization rate is 90%, that is to say that 90% of the amount of Na 2 O added (per minute) are neutralized.

    Le taux de consolidation, à l'issue de cette addition simultanée, est égal à 19,5.The consolidation rate, after this simultaneous addition, is equal to 19.5.

    Après introduction de la totalité du silicate, on continue à introduire la solution d'acide sulfurique, au même débit, et ceci pendant 10 mn. Cette introduction complémentaire d'acide amène alors le pH du milieu réactionnel à une valeur ègale à 4,5.After introduction of all of the silicate, the introduction of the sulfuric acid solution, at the same flow rate, for 10 min. This additional introduction of acid then brings the pH of the reaction medium to a value equal to 4.5.

    On laisse ensuite mûrir le milieu réactionnel pendant 10 mn (sous agitation, à 95 °C).The reaction medium is then left to mature for 10 min (with stirring, at 95 ° C).

    On obtient ainsi une bouillie de silice précipitée qui est filtrée et lavée au moyen d'un filtre rotatif sous vide de telle sorte que l'on récupère finalement un gâteau de silice dont la perte au feu est de 87 % (donc un taux de matière sèche de 13 % en poids). A precipitated silica slurry is thus obtained which is filtered and washed with by means of a rotary vacuum filter so that we finally recover a silica cake with a loss on ignition of 87% (therefore a dry matter content 13% by weight).

    Ce gâteau est ensuite fluidifié par simple action mécanique. Après cette opération de délitage, la bouillie résultante est atomisée au moyen d'un atomiseur à turbines.This cake is then fluidized by simple mechanical action. After this disintegration operation, the resulting slurry is atomized by means of an atomizer with turbines.

    Les caractéristiques de la silice P5 sous forme de poudre (conforme à l'invention) sont alors les suivantes :

    • surface spécifique CTAB   118 m2/g
    • surface spécifique BET   160 m2/g
    • volume poreux V1 représenté
      par les pores de d ≤ 400 Å   0,48 cm3/g
    • volume poreux V2 représenté
      par les pores 175 Å ≤ d ≤ 275 Å   0,11 cm3/g
    • rapport V2/V1   23 %
    • taille moyenne des particules   60 µm
    The characteristics of the silica P5 in powder form (according to the invention) are then as follows:
    • specific surface CTAB 118 m 2 / g
    • BET specific surface 160 m 2 / g
    • pore volume V1 shown
      through pores of d ≤ 400 Å 0.48 cm 3 / g
    • pore volume V2 shown
      through pores 175 Å ≤ d ≤ 275 Å 0.11 cm 3 / g
    • V2 / V1 ratio 23%
    • average particle size 60 µm

    On soumet la silice P5 au test de désagglomération tel que défini précédemment dans la description.The silica P5 is subjected to the deagglomeration test as defined earlier in the description.

    Après désagglomération aux ultra-sons, elle présente un diamètre médian (⊘50) de 2,6 µm et un facteur de désagglomération aux ultra-sons (FD) de 4,2 ml.After ultrasonic deagglomeration, it has a median diameter (⊘ 50 ) of 2.6 μm and an ultrasonic deagglomeration factor (F D ) of 4.2 ml.

    EXEMPLE 6EXAMPLE 6

    Dans un réacteur en acier inoxydable muni d'un système d'agitation par hélices et d'un chauffage par double enveloppe, on introduit :

    • 626 litres d'eau, et
    • 36 litres d'une solution de silicate de sodium (de rapport molaire SiO2/Na2O égal à 3,6) ayant une concentration exprimée en silice de 130 g/l.
    In a stainless steel reactor provided with a propeller stirring system and a jacket heating:
    • 626 liters of water, and
    • 36 liters of a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3.6) having a concentration expressed as silica of 130 g / l.

    La concentration en silicate exprimée en SiO2 dans le pied de cuve initial est donc de 7,1 g/l. La solution est alors portée à une température de 95 °C tout en la maintenant sous agitation. L'ensemble de la réaction est effectué à 95 °C. On y introduit ensuite, pendant 3 mn et 20 s, une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 5,4 l/mn ; à l'issue de cette addition, le taux de neutralisation du pied de cuve est de 67 %, c'est-à-dire que 67 % de la quantité de Na2O présente dans le pied de cuve initial sont neutralisés.The silicate concentration expressed as SiO 2 in the initial base stock is therefore 7.1 g / l. The solution is then brought to a temperature of 95 ° C. while keeping it under stirring. The whole reaction is carried out at 95 ° C. Then there is introduced, for 3 min and 20 s, a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 5.4 l / min; at the end of this addition, the neutralization rate of the base stock is 67%, that is to say that 67% of the amount of Na 2 O present in the initial base stock is neutralized.

    On introduit ensuite simultanément, pendant 70 mn, dans le milieu réactionnel :

    • une solution d'acide sulfurique, de concentration égale à 80 g/l, à un débit de 5,4 l/mn, et
    • une solution de silicate de sodium, de concentration exprimée en silice égale à 130 g/l, à un débit de 8,8 l/mn.
    Then introduced simultaneously, for 70 min, into the reaction medium:
    • a sulfuric acid solution, concentration equal to 80 g / l, at a flow rate of 5.4 l / min, and
    • a sodium silicate solution, concentration expressed as silica equal to 130 g / l, at a flow rate of 8.8 l / min.

    Lors de cette addition simultanée, le taux de neutralisation instantané est de 83 %, c'est-à-dire que 83 % de la quantité de Na2O ajoutée (par mn) sont neutralisés.During this simultaneous addition, the instantaneous neutralization rate is 83%, that is to say that 83% of the amount of Na 2 O added (per minute) are neutralized.

    Le taux de consolidation, à l'issue de cette addition simultanée, est égal à 17,1.The consolidation rate, after this simultaneous addition, is equal to 17.1.

    Après introduction de la totalité du silicate, on continue à introduire la solution d'acide sulfurique, au même débit, et ceci pendant 10 mn. Cette introduction complémentaire d'acide amène alors le pH du milieu réactionnel à une valeur égale à 4,5.After introduction of all of the silicate, the introduction of the sulfuric acid solution, at the same flow rate, for 10 min. This additional introduction of acid then brings the pH of the reaction medium to a value equal to 4.5.

    On laisse ensuite mûrir le milieu réactionnel pendant 10 mn (sous agitation, à 95 °C)The reaction medium is then left to mature for 10 min (with stirring, at 95 ° C)

    On obtient ainsi une bouillie de silice précipitée qui est filtrée et lavée au moyen d'un filtre presse de telle sorte que l'on récupère finalement un gâteau de silice dont la perte au feu est de 78 % (donc un taux de matière sèche de 22 % en poids).A precipitated silica slurry is thus obtained which is filtered and washed with using a filter press so that a cake is finally recovered silica with a loss on ignition of 78% (therefore a dry matter rate of 22% in weight).

    Ce gâteau est ensuite fluidifié par action mécanique et chimique (ajout d'une quantité d'aluminate de sodium correspondant à un rapport pondéral Al/SiO2 de 3000 ppm). Après cette opération de délitage, on obtient un gâteau pompable, de pH égal à 6,7, qui est alors atomisé au moyen d'un atomiseur à buses.This cake is then fluidized by mechanical and chemical action (addition of a quantity of sodium aluminate corresponding to a weight ratio Al / SiO 2 of 3000 ppm). After this disintegration operation, a pumpable cake is obtained, with a pH equal to 6.7, which is then atomized by means of a nozzle atomizer.

    Les caractéristiques de la silice P6 sous forme de billes sensiblement sphériques (conforme à l'invention) sont alors les suivantes :

    • surface spécifique CTAB   131 m2/g
    • surface spécifique BET   145 m2/g
    • volume poreux V1 représenté
      par les pores de d ≤ 400 Å   0,84 cm3/g
    • volume poreux V2 représenté
      par les pores 175 Å ≤ d ≤ 275 Å   0,40 cm3/g
    • rapport V2/V1   48 %
    • taille moyenne des billes   200 µm
    The characteristics of the silica P6 in the form of substantially spherical beads (in accordance with the invention) are then as follows:
    • CTAB specific surface 131 m 2 / g
    • BET specific surface 145 m 2 / g
    • pore volume V1 shown
      through pores of d ≤ 400 Å 0.84 cm 3 / g
    • pore volume V2 shown
      through pores 175 Å ≤ d ≤ 275 Å 0.40 cm 3 / g
    • V2 / V1 ratio 48%
    • average bead size 200 µm

    On soumet la silice P6 au test de désagglomération tel que défini précédemment dans la description.The silica P6 is subjected to the deagglomeration test as defined earlier in the description.

    Après désagglomération aux ultra-sons, elle présente un diamètre médian (Ø50) de 3,7 µm et un facteur de désagglomération aux ultra-sons (FD) de 11,0 ml. After ultrasonic deagglomeration, it has a median diameter (Ø 50 ) of 3.7 μm and an ultrasonic deagglomeration factor (F D ) of 11.0 ml.

    EXEMPLE 7EXAMPLE 7

    Dans un réacteur en acier inoxydable muni d'un système d'agitation par hélices et d'un chauffage par double enveloppe, on introduit :

    • 853 litres d'eau,
    • 18,4 litres d'une solution de silicate de sodium (de rapport molaire SiO2/Na2O égal à 3,5) ayant une concentration exprimée en silice de 237 g/l.
    In a stainless steel reactor provided with a propeller stirring system and a jacket heating:
    • 853 liters of water,
    • 18.4 liters of a sodium silicate solution (SiO 2 / Na 2 O molar ratio equal to 3.5) having a concentration expressed as silica of 237 g / l.

    La concentration en silicate exprimée en SiO2 dans le pied de cuve initial est donc de 5 g/l. La solution est alors portée à une température de 85 °C tout en la maintenant sous agitation. L'ensemble de la réaction est effectué à 85 °C sous agitation. On y introduit ensuite, pendant 3 mn et 20 s, de l'acide sulfurique dilué, de densité à 20 °C égale à 1,050, à un débit de 4,8 l/mn ; à l'issue de cette addition, le taux de neutralisation du pied de cuve est de 91 %, c'est-à-dire 91 % de la quantité de Na2O présente dans le pied de cuve initial sont neutralisés.The silicate concentration expressed as SiO 2 in the initial base stock is therefore 5 g / l. The solution is then brought to a temperature of 85 ° C. while keeping it under stirring. The entire reaction is carried out at 85 ° C. with stirring. Then, for 3 min and 20 s, dilute sulfuric acid, with a density at 20 ° C. equal to 1.050, is introduced therein at a flow rate of 4.8 l / min; at the end of this addition, the neutralization rate of the base stock is 91%, that is to say 91% of the amount of Na 2 O present in the initial base stock is neutralized.

    On introduit ensuite simultanément, pendant 60 mn, dans le milieu réactionnel une solution de silicate de sodium du type décrit ci-avant, à un débit de 5,4 l/mn, et de l'acide sulfurique dilué également du type décrit ci-avant, à un débit régulé de manière à maintenir, dans le milieu réactionnel, le pH :

    • à une valeur de 8,5 ± 0,1 pendant les 15 premières minutes, puis
    • à une valeur de 7,8 ± 0,1 pendant les 45 dernières minutes.
    Then introduced simultaneously, for 60 min, into the reaction medium a sodium silicate solution of the type described above, at a flow rate of 5.4 l / min, and dilute sulfuric acid also of the type described above. before, at a regulated flow rate so as to maintain, in the reaction medium, the pH:
    • at a value of 8.5 ± 0.1 for the first 15 minutes, then
    • at a value of 7.8 ± 0.1 during the last 45 minutes.

    Lors de cette addition simultanée, le taux de neutralisation instantané est de 92 %, c'est-à-dire que 92 % de la quantité de Na2O ajoutée (par mn) sont neutralisés.During this simultaneous addition, the instantaneous neutralization rate is 92%, that is to say that 92% of the amount of Na 2 O added (per minute) are neutralized.

    Le taux de consolidation, à l'issue de cette addition simultanée, est égal à 17,5.The consolidation rate, after this simultaneous addition, is equal to 17.5.

    Après cette addition simultanée, on arrête l'introduction de silicate et on continue à introduire l'acide sulfurique dilué de façon à faire décroítre la valeur du pH du milieu réactionnel jusqu'à une valeur égale à 4,4 en 7 mn.After this simultaneous addition, the introduction of silicate is stopped and continues to introduce dilute sulfuric acid so as to decrease the value of pH of the reaction medium up to a value equal to 4.4 in 7 min.

    On arrête ensuite l'introduction d'acide, puis on maintient le mélange réactionnel sous agitation pendant 10 mn à une température de 85 °C.The introduction of acid is then stopped, and the mixture is maintained reaction with stirring for 10 min at a temperature of 85 ° C.

    On obtient ainsi une bouillie de silice précipitée qui est filtrée et lavée au moyen d'un filtre presse de telle sorte que l'on récupère finalement un gâteau de silice dont la perte au feu est de 81 % (donc un taux de matière sèche de 19 % en poids).A precipitated silica slurry is thus obtained which is filtered and washed with using a filter press so that a cake is finally recovered silica with a loss on ignition of 81% (therefore a dry matter rate of 19% in weight).

    Ce gâteau est ensuite fluidifié par action mécanique et chimique (ajout d'une quantité d'aluminate de sodium correspondant à un rapport pondéral Al/SiO2 de 2500 ppm et ajout d'acide sulfurique). Après cette opération de délitage, on obtient un gâteau pompable, de pH égal à 6,5, qui est alors atomisé au moyen d'un atomiseur à buses.This cake is then fluidized by mechanical and chemical action (addition of a quantity of sodium aluminate corresponding to an Al / SiO 2 weight ratio of 2500 ppm and addition of sulfuric acid). After this disintegration operation, a pumpable cake is obtained, with a pH equal to 6.5, which is then atomized by means of a nozzle atomizer.

    Les caractéristiques de la silice P7 sous forme de billes sensiblement sphériques (conforme à l'invention) sont alors les suivantes :

    • surface spécifique CTAB   123 m2/g
    • surface spécifique BET   136 m2/g
    • volume poreux V1 représenté
      par les pores de d ≤ 400 Å   0,77 cm3/g
    • volume poreux V2 représenté
      par les pores 175 Å ≤ d ≤ 275 Å   0,21 cm3/g
    • rapport V2/V1   27 %
    • taille moyenne des billes   250 µm
    The characteristics of silica P7 in the form of substantially spherical beads (in accordance with the invention) are then as follows:
    • specific surface CTAB 123 m 2 / g
    • BET specific surface area 136 m 2 / g
    • pore volume V1 shown
      through pores of d ≤ 400 Å 0.77 cm 3 / g
    • pore volume V2 shown
      through pores 175 Å ≤ d ≤ 275 Å 0.21 cm 3 / g
    • V2 / V1 ratio 27%
    • average bead size 250 µm

    On soumet la silice P7 au test de désagglomération tel que défini précédemment dans la description.The silica P7 is subjected to the deagglomeration test as defined earlier in the description.

    Après désagglomération aux ultra-sons, elle présente un diamètre médian (⊘50) de 2,9 µm et un facteur de désagglomération aux ultra-sons (FD) de 14,5 ml.After ultrasonic deagglomeration, it has a median diameter (⊘ 50 ) of 2.9 µm and an ultrasonic deagglomeration factor (F D ) of 14.5 ml.

    EXEMPLE 8EXAMPLE 8

    A titre comparatif, trois silices commerciales, de surface spécifique CTAB comprise entre 100 et 140 m2/g, utilisables comme charges renforçantes pour élastomères, ont été étudiées. Il s'agit :

    • d'une part, de deux silices sous forme de poudre :
      • la poudre PERKASIL KS® 300 (référencée PC1 ci-dessous), vendue par la Société AKZO,
      • la poudre ULTRASIL VN2® (référencée PC2 ci-dessous), vendue par la Société DEGUSSA,
    • d'autre part, d'une silice sous forme de billes sensiblement sphériques, la silice ZEOSIL® 125 MP (référencée MP1 ci-dessous) vendue par la Société RHONE-POULENC CHIMIE.
    By way of comparison, three commercial silicas, with a CTAB specific surface of between 100 and 140 m 2 / g, which can be used as reinforcing fillers for elastomers, have been studied. It's about :
    • on the one hand, two silicas in powder form:
      • PERKASIL KS® 300 powder (referenced PC1 below), sold by AKZO,
      • ULTRASIL VN2® powder (referenced PC2 below), sold by the company DEGUSSA,
    • on the other hand, a silica in the form of substantially spherical beads, the ZEOSIL® 125 MP silica (referenced MP1 below) sold by the company RHONE-POULENC CHIMIE.

    Les caractéristiques de ces silices sont rassemblées dans le tableau I ci-dessous. Ce tableau reprend également, pour comparaison, les caractéristiques des silices P1 à P7 selon l'invention.

    Figure 00230001
    The characteristics of these silicas are collated in Table I below. This table also shows, for comparison, the characteristics of the silicas P1 to P7 according to the invention.
    Figure 00230001

    EXEMPLE 9EXAMPLE 9

    Cet exemple illustre l'utilisation et le comportement de silices selon l'invention et de silices de l'art antérieur dans une formulation pour caoutchouc industriel.This example illustrates the use and behavior of silicas according to the invention and prior art silicas in a formulation for rubber industrial.

    On utilise la formulation suivante (en parties, en poids) :

    • Caoutchouc S.B.R. 1712 (1)    100
    • Silice   51
    • ZnO actif (2)    1,81
    • Acide stéarique   0,35
    • 6PPD (3)    1,45
    • CBS (4)    1,3
    • DPG (5)    1,45
    • Soufre (6)    1,1
    • Silane X50S (7)    8,13
    The following formulation is used (in parts, by weight):
    • SBR 1712 rubber (1) 100
    • Silica 51
    • Active ZnO (2) 1.81
    • Stearic acid 0.35
    • 6PPD (3) 1.45
    • CBS (4) 1.3
    • DPG (5) 1.45
    • Sulfur (6) 1.1
    • Silane X50S (7) 8.13

    Les formulations sont préparées de la manière suivante :The formulations are prepared as follows:

    Dans un mélangeur interne (type BANBURY), on introduit dans cet ordre et aux temps et températures du mélange indiqués entre parenthèses :

    • du SBR 1712 (to)(55 °C)
    • le X50S et les 2/3 de la silice (t0 + 1 mn)(90 °C)
    • le ZnO, l'acide stéarique, le 6PPD et 1/3 de la silice (to + 2 mn)(110 °C)
    In an internal mixer (BANBURY type), the following are introduced in this order and at the times and temperatures of the mixture indicated in parentheses:
    • SBR 1712 (t o ) (55 ° C)
    • X50S and 2/3 of the silica (t 0 + 1 min) (90 ° C)
    • ZnO, stearic acid, 6PPD and 1/3 of silica (t o + 2 min) (110 ° C)

    La décharge du mélangeur (tombée du mélange) se fait quand la température de la chambre atteint 165 °C (c'est-à-dire, à peu près to + 5 mn). Le mélange est introduit dans un mélangeur à cylindres, maintenus à 30 °C, pour y être calandré. Dans ce mélangeur, on introduit le CBS, le DPG et le soufre. The discharge of the mixer (falling of the mixture) takes place when the temperature of the chamber reaches 165 ° C. (that is to say, approximately t o + 5 min). The mixture is introduced into a cylinder mixer, maintained at 30 ° C., to be calendered there. CBS, DPG and sulfur are introduced into this mixer.

    Après homogénéisation et trois passages au fin, le mélange final est calandré sous la forme de feuilles de 2,5 à 3 mm d'épaisseur.After homogenization and three passages at the end, the final mixture is calendered in the form of sheets 2.5 to 3 mm thick.

    Les résultats des essais sont les suivants :The results of the tests are as follows:

    1- Propriétés rhéologiques 1- Rheological properties

    Les mesures sont réalisées sur les formulations à l'état cru à 150 °C.The measurements are carried out on the formulations in the raw state at 150 ° C.

    Les résultats sont reportés dans le tableau II ci-dessous. On a indiqué l'appareillage utilisé pour conduire les mesures. P1 P4 P5 P6 PC1 PC2 MP1 Couple mini 22,6 21,1 22,6 18,9 28,9 23,2 31,2 Couple maxi 70,9 69,7 70,5 69,8 82,7 79,7 86,7 The results are reported in Table II below. The apparatus used to conduct the measurements was indicated. P1 P4 P5 P6 PC1 PC2 MP1 Mini couple 22.6 21.1 22.6 18.9 28.9 23.2 31.2 Max torque 70.9 69.7 70.5 69.8 82.7 79.7 86.7

    Les formulations obtenues à partir de silices selon l'invention conduisent aux valeurs les plus faibles.The formulations obtained from silicas according to the invention lead at the lowest values.

    Ceci traduit une plus grande facilité de mise en oeuvre des mélanges préparés à partir des silices selon l'invention, en particulier au niveau des opérations d'extrusion et de calandrage souvent réalisées lors de la confection des pneumatiques (moindre dépense d'énergie pour mettre en oeuvre le mélange, plus grande facilité d'injection lors du mélangeage, moindre gonflement en filière lors de l'extrusion, moindre retrait au calandrage, ...).This reflects a greater ease of implementation of the mixtures prepared from the silicas according to the invention, in particular at the level of extrusion and calendering operations often carried out during manufacture tires (lower energy expenditure to implement the mixing, greater ease of injection during mixing, less swelling in the die during extrusion, less shrinkage in calendering, ...).

    2- Propriétés mécaniques 2- Mechanical properties

    Les mesures sont réalisées sur les formulations vulcanisées.The measurements are carried out on the vulcanized formulations.

    La vulcanisation est réalisée en portant les formulations à 150 °C pendant 40 minutes.Vulcanization is carried out by bringing the formulations to 150 ° C. for 40 minutes.

    Les normes suivantes ont été utilisées :

  • (i) essais de traction (module 100 %, résistance à la rupture, allongement à la rupture) :
  • NFT 46-002 ou ISO 37-1977
  • (ii) essais de résistance au déchirement
  • DIN 53-507
    • The following standards have been used:
  • (i) tensile tests (100% modulus, breaking strength, elongation at break):
  • NFT 46-002 or ISO 37-1977
  • (ii) tear resistance tests
  • DIN 53-507

    • Les résultats obtenus sont consignés dans le tableau III ci-dessous. P1 P4 P5 P6 PC1 PC2 MP1 Module 100 % (MPa) 2,2 2,4 2,4 1,8 3,3 2,7 3,8 Résistance rupture (MPa) 22,3 20,7 22,5 24,9 19,2 20,2 19,5 Allongement rupture (%) 490 470 500 593 397 419 375 Résistance déchirement (kN/m) 20,0 16,3 27,2 27,4 11,5 14,3 9,7 The results obtained are reported in Table III below. P1 P4 P5 P6 PC1 PC2 MP1 100% module (MPa) 2.2 2.4 2.4 1.8 3.3 2.7 3.8 Breaking strength (MPa) 22.3 20.7 22.5 24.9 19.2 20.2 19.5 Elongation at break (%) 490 470 500 593 397 419 375 Tear strength (kN / m) 20.0 16.3 27.2 27.4 11.5 14.3 9.7

    Les résultats ci-dessus mettent clairement en évidence le meilleur effet de renforcement conféré par les silices selon l'invention par rapport à des silices de l'art antérieur de pouvoir renforçant théorique pourtant équivalent.The above results clearly highlight the best effect of reinforcement conferred by the silicas according to the invention compared to silicas of the prior art of theoretical reinforcing power, however equivalent.

    Les silices selon l'invention conduisent aux modules 100% les plus faibles, preuve d'une meilleure dispersion de la silice.The silicas according to the invention lead to the weakest 100% modules, evidence of better dispersion of silica.

    Le plus haut pouvoir renforçant des silices selon l'invention est notamment confirmé par les valeurs plus élevées obtenues pour la résistance à la rupture et au déchirement et pour l'allongement à la rupture.The highest reinforcing power of silicas according to the invention is in particular confirmed by the higher values obtained for the breaking strength and for tearing and for elongation at break.

    Claims (16)

    1. Precipitated silica characterized in that it has:
      a CTAB specific surface area (SCTAB) of between 100 and 140 m2/g,
      a pore distribution such that the pore volume formed by the pores whose diameter is between 175 and 275 Å represents less than 50% of the pore volume formed by the pores having diameters less than or equal to 400 Å,
      a median diameter (50), after deagglomeration by ultrasound, of less than 4.5 µm,
      and is in at least one of the following forms: approximately spherical beads having a mean size of at least 80 µm; a powder having a mean size of at least 15 µm; granules having a size of at least 1 mm.
    2. Silica according to claim 1, characterized in that it has an ultrasound deagglomeration factor (FD) greater than 3.0 ml.
    3. Silica according to either of claims 1 and 2, characterized in that it is in the form of approximately spherical beads having a mean size of at least 80 µm and in that it has a median diameter (⊘50), after ultrasound deagglomeration, of less than 3.1 µm and an ultrasound deagglomeration factor (FD) greater than 8 ml.
    4. Silica according to one of claims 1 to 3, characterized in that it has a BET specific surface area (SBET) of between 100 and 210 m2/g.
    5. Silica according to one of claims 1 to 4, characterized in that it has an SBET/SCTAB ratio of between 1.0 and 1.2.
    6. Silica according to one of claims 1 to 4, characterized in that it has an SBET/SCTAB ratio greater than 1.2.
    7. Silica according to one of claims 1 to 6, characterized in that it has a DOP oil uptake of between 150 and 400 ml/100 g.
    8. Method of preparing a silica according to one of claims 1 to 7, of the type comprising the reaction of an alkali metal M silicate with an acidifying agent, whereby a suspension of precipitated silica is obtained, then the separation and drying of this suspension, characterized in that the precipitation is carried out in the following manner:
      (i) an initial stock is formed, which comprises part of the total amount of the alkali metal M silicate involved in the reaction, the concentration of silicate expressed as SiO2 in the said stock being at most 11 g/l,
      (ii) the acidifying agent is added to the said initial stock until at least 50% of the amount of M2O present in the said initial stock is neutralized; and
      (iii) some acidifying agent and the remaining amount of alkali metal M silicate are added simultaneously to the reaction mixture such that the amount of silicate added (expressed as SiO2)/amount of silicate present in the initial stock (expressed as SiO2) ratio is between 12 and 100.
    9. Method according to claim 8, characterized in that, in step (iii), some acidifying agent and the remaining amount of alkali metal M silicate are added simultaneously to the reaction mixture so that the amount of silica added/amount of silica present in the initial stock ratio is between 12 and 50.
    10. Method according to either of claims 8 and 9, characterized in that, after step (iii), an additional amount of acidifying agent is added to the reaction mixture, preferably so as to obtain a pH value of the reaction mixture of between 3 and 6.5.
    11. Method according to one of claims 8 to 10, characterized in that, throughout step (iii), the amount of acidifying agent added is such that 80 to 99% of the amount of M2O added is neutralized.
    12. Method according to one of claims 8 to 11, characterized in that no electrolyte is used.
    13. Method according to one of claims 8 to 12, characterized in that the said drying is spray drying.
    14. Method according to claim 13, characterized in that the dried product is then agglomerated.
    15. Method according to claim 14, characterized in that the dried product is then milled and then, optionally, agglomerated.
    16. Use of a silica according to one of claims 1 to 7 as a reinforcing filler for elastomers.
    EP94928935A 1993-09-29 1994-09-29 Precipitated silica Expired - Lifetime EP0670814B1 (en)

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    PCT/FR1994/001144 WO1995009128A1 (en) 1993-09-29 1994-09-29 Precipitated silica

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    EP0670814A1 (en) 1995-09-13
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    JPH08501527A (en) 1996-02-20
    WO1995009128A1 (en) 1995-04-06
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    FI952606A0 (en) 1995-05-29
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    CA2150368C (en) 2001-05-01
    FR2710630A1 (en) 1995-04-07

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